Let's take a look at ogres and half-ogres:
Half-Ogre: +6 Str, -2 Dex, +2 Con, -2 Int, -2 Cha, Favored: Barbarian, Large, 30' speed, Darkvision 60, +4 natural armor, +2 LA.
Ogre: +10 Str, -2 Dex, +4 Con, -4 Int, -4 Cha, Favored: Barbarian, Large, 30' speed, Darkvision 60, +5 natural armor, Weapon/armor proficiencies, +2 LA, 4 HD.
The Difference: +4 Str, +2 Con, -2 Int, -2 Cha, +1 NA, Weapon/armor proficiencies, 4 HD.
Based on that, I'd say that a hypothetical race with +4 Str, +2 Con, -2 Int, -2 Cha, and +1 NA would be LA +1, wouldn't you? As a matter of fact, it is--the Gnoll, which gets those exact benefits for +1 LA and 2 HD.
So those benefits are worth the loss of 3 levels, right? Well, apparently not, because the Ogre is stuck with 4 HD. The Ogre gets the short end of the stick because he's more monstrous-looking; thus they discourage you from playing Ogres by sinking more of your levels into racial hit dice rather than LA. Which is more accurate? I'd say the Gnoll, because those 4 HD are absolutely useless to you. Hell, a half-ogre gnoll is weirder than an ogre, yet because both are individually less weird than an ogre, they come out a level ahead!
The racial hit dice for Giant (the Ogre's racial HD) give you 3/4 BAB, good Fort, 2+Int skill points, simple and martial weapons, light and medium armors, shields, and d8 HP...meaning that having Giant RHD is worse than the fighter class chassis. That's right, worse than the
fighter. That's a good enough reason to get rid of the RHD, for me at least, and either bump the LA up by one if you want or simply ignore the change entirely. You're already behind enough with an LA, since class benefits scale and racial ones don't, so why sink them further into the hole with more useless HD?
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Theoretically, +1 LA = 2 RHD, so +1 LA/2 RHD == 4 RHD.
In theory, this works out nicely, but let's face it: the only thing that really matters is how soon you get to your actual class abilities--yeah, having 2 HD worth of BAB. saves, and HP is better than not have those 2 HD, but given the choice between LA +3 and 6 RHD, or LA +1 and 2 RHD, or any other combination I'd choose LA because (A) I get class abilities faster and (B) I can buy off LA to become level-appropriate where I can't do the same for RHD.
Let's say you want to make a wizard. You have several choices: you can play...
- ...a Wizard 1/LA 2 in a party of 3rd level characters, in which case your 7 HP and 3 spells per day will make you far too fragile and useless;
- ...a Wizard 1/LA 1/Expert 2 in a party of 4th level characters, in which case you can survive fairly well but can't contribute much to the party;
- ...a Wizard 1/Expert 4 in a party of 5th level characters, in which case you're more durable but play as a "wizard" in name only; or
- ...a Wizard 5 in a party of 5th level characters, in which case you have 3rd level spells and can actually pull your weight.
Let's say you want to make a fighter. You have several choices: you can play...
- ...a Fighter 1/LA 2 in a party of 3rd level characters, in which case your lower HP pretty much force you to focus on ranged combat, since you can't survive in melee all that well;
- ...a Fighter 1/LA 1/Expert 2 in a party of 4th level characters, in which case you can survive fairly well but lose out on what few class features you have;
- ...a Fighter 1/Expert 4 in a party of 5th level characters, in which case you have the feats and BAB of a fighter of half your level; or
- ...a Fighter 5 in a party of 5th level characters, in which case you have good BAB and HD and might actually have enough feats to work on starting a feat chain.