Few things to note about dragon PCs.
1) As PCs (or cohorts), you are expected to use the same stat generation method as the rest of your players (be it rolling or point buy) and allow them access to gear as a PC. If you ran the dragon right out of the MM, this means its stats would be way weaker than it should be. With 28 point buy, you would be shortchanging the dragon of roughly 4 points in str/dex/con/int (more with gear).
2) Dragon PCs aren't really formidable in combat, their usefulness lies in their other abilities like skills, movement modes, flight, senses and alternate breath weapons. They will be slaughtered in straight melee, which is why I suggested tricking out its breath weapon. Yes, this does risk making it a 1-trick pony, but at least it should be an effective one.
Here is a small excerpt regarding a friend's experiences with a dragon cohort.
[Sblock]The silver dragon in my campaign is actually an NPC, a cohort of the PC wizard. She started off as his dragon familiar (using the Dragon Familiar feat) and then became his dragon cohort (using the Dragon Cohort feat). So she started pretty weak and has slowly caught up to the rest of the party (at least to the other party members; the wizard actually has pulled ahead because his player does so much roleplaying and storyline stuff). The wizard's player has been very paranoid about exposing her to danger. She usually flies by and breathes with Maximize Breath. Only now is he realizing that she's turned into a tank, with by far the best AC and the second most hit points. I think he's going to put the
wild special ability on her
belt of giant strength and
cloak of resistance. Up until now she's been heavily overshadowed in melee by the party's half-celestial, but I think she's starting to catch up, and will get even better at he next level because her damage will increase with her size.
She's also fairly versatile, and has by far the best assortment of skills in the party. She has 11 skills maxed out: Appraise, Knowledge (arcana, geography, nature), Listen, Search, Sense Motive, Spot, Swim (cross class), Tumble (cross class), and Use Magic Device. The party has given her
cure wands,
magic missile wands, and even their
staff of life. They made a staff of revivification and mass heal and gave it to her too. (She has clerical spells on her spell list, so she can use them even without Use Magic Device.) So she's often played the roll of advance scout and healer. She's frankly the only party member who actually knows how to get to the Labyrinth where they're headed, from her Knowledge (geography) (the NPC captain of their boat knows the way too), and she's the one who appraises all the party's treasure. I'd say that her role until now probably wouldn't satisfy most players, but then if a player had actually been playing her as a PC, she'd have seen more melee and focused much earlier on getting those wild magic items to buff her in combat. Several party members have +5 weapons, and indeed have had them for a while, but she's got only a
+3 amulet of mighty fists. If a player had been running her, she's probably have a +5 amulet by now. If she had the +5 amulet and the +6 wild belt of giant strength, her attack bonus would rise above 30 (at only 15 hit dice).
I think probably since her natural weapons (other than the bite) don't do as much damage as the best manufactured melee weapons that she probably wouldn't deal out quite as much damage as a melee specialist of her ECL. When she gets to 22nd level and increases to large size, however, her bite will do the same damage as a large greatsword (but without the 1.5x Strength or 2x Power Attack alas), her claws will do the same damage as medium longswords (but with only .5x Strength), her wings will do the same damage as medium short swords, and her tail will do the same as a medium longsword but with 1.5x Strength and 2x Power Attack. When she gets her next feat at 24th level the tail will do damage like a medium greatsword. Since she just took Multiattack, her secondary attack will suffer only a -2 penalty. So they even have a benefit over iterative attacks with a manufacture weapon (plus she needs only one magic item to make them all magical and give them an enhancement bonus to their attack and damage rolls).
I think that she's probably not going to get as good in melee as the party's half-celestial barbarian2/cleric1/ranger2/fighter4/lightning warrior8, but I think she might do in melee as well as the party's half-celestial monk 17. She's certainly more versatile than the monk.
She's also gotten her own 1st-level spells now. We gave her
guiding light to help the party's archer because the wizard's player has seen her mostly as an auxiliary, not a main combatant, having trouble seeing her as having grown well beyond his small-sized familiar. We did give her true strike, however, so that gives her a benefit that the half-celestial combat specialists in the campaign don't have.
Her big weakness, of course, is fire. "Dragons: color-coded for your convenience." (Order of the Stick)
She has decent but not outstanding saves. Once the wizard gets the wild ability on her cloak of resistance and boots it from +3 to +5, she's actually going to have the second-best Will save in the party. She has excellent ability scores: Str, Int and Wis all 26, Cha 24, Con 22, Dex 20. Even without the cloak she has the third-best Fort save in the party.
She has died twice. The first time, when I think she was still a wyrmling, a group of kobold elite scouts shot her out of the sky when she was spotting for the party's spellcasters. The arrows knocked her unconscious, and the fall killed her. Ever since, the wizard's player has been paranoid about her dying again, and that's why he gave her the
+6 bracers of armor and the
+4 ring of protection. Her low touch AC--he has visions of her getting disintegrated--motivated him to bump her
+4 gloves of Dexterity (useful only in her humanoid forms) into
+6 wild gloves of Dexterity. The second time she died, a kobold sorcerer and cronies nuked the party with delayed-blast fireballs. The wizard died too. The dragon's vulnerability to fire definitely played a role. I think had she not had the vulnerability she wouldn't have died then. Oddly enough he has done nothing to try to shore up her vulnerabilities, say, by getting her a
ring of fire resistance or a
ring of featherfalling. (I think though that he might have started carrying around a
featherfall spell.
Even the push for the
wild gloves, belt and cloak have come from me. He's been pretty content to have her fly out of range of danger. One day the ship they had taken from epic pirates got its rudder snagged. She and the half-celestial lightning warrior went underwater to check it out. A group of dire sharks swarmed them. The player was so afraid that she would get grabbed and pulled into the depths to drown that he had her swim to the surface and fly out of their reach on her first turn, leaving the half-celestial alone underwater to fend for himself. Then about 30 sahuagin swarmed over the sides of the ship, so the rest of the party stayed occupied trying to protect their crew from dying at the hands of the sahuagin and effectively rendering the ship immobile, so nobody came to the aid of the half-celestial. I think someone playing the dragon as a PC would have had a better idea of her capabilities and might not have had her flee, but he still thought of her as his little wyrmling.
I started playing a red dragon hatchling at 1st level under the Savage Species rules in the Shackled City Adventure Path. (Like so many other campaigns, it lasted only a couple of levels.) Dragon issue 332 contained the level advancement tables for the chromatic dragons. I think I got to 3rd level, which is where the red hatchling gets flight. I found that at first level he did at least as well in melee as the party's paladin, and probably better. He did decent damage and had good hit points. We fought a grell or something like that that floated down, grabbed one of the other PCs, and floated up out of range with him. It was very frustrating that my dragon couldn't fly--and didn't have any ranged attacks either at that level. (The red dragon doesn't get a breath weapon until 10th level [7 hit dice].) It was nice when he got flight at 3rd level. We never did encounter any cold damage, so his big vulnerability didn't come into play. Indeed we rarely had to make any saving throws at those levels, but he did have good bonuses. I think he had to wear barding as a hatchling starts without any natural armor. I think though that I put his highest or second-highest ability score in Dexterity too.
I suspect that a dragon PC compares favorably at very low levels, then maybe starts to sag a bit, but then later compares favorably again.[/Sblock]
Hope it helps. Or at least makes for an entertaining read.