I got up to 14th level as a generalist wizard, and I loved it.
-Having the ability to research and buy spells makes wiz's have an edge in the versatility category.
-The counter to this being affording the time or money to do either, I more enjoyed the freedom and option of one day researching spells and buying that next spell to be just as enjoyable as actually doing so.
-Being able to scribe scrolls as a free feat pretty much negates the sorceror's ability to cast mucho spells per day, and cast whatever he wants. If I want the option of casting any spell in my library- I just scribe em.
-The counter to this being, again, the sheer economic weight of this. So- I still find it sufficient to just scribe combat spells.
-Being the brains is great in a party. Ya never have to pause and ask yourself if your character will think what you do.
-Knowledge skills. Oh boy I miss those now.
-The spells are flashy, and they directly impact your enemy- which in turn means you can stand up to people with a smile that you've got three disintegrates in hand and the capability to summon a Celestial Dire Bear on standby (and smile at them from 40 ft to the right thanks to mislead).
-Extending this into the realm of roleplay, being a wizard can be very gratifying. Standing down an entire contingent of Roman-esque scouts after hovering down before them (as they know you're a powerful wizard) and making them all turn and retreat with no more than a word or two is very, very cool.
-Alternatively, the possibility of being mauled in one round by something you aren't prepared for (regardless of your level- thanks d4 HD!) is a perfectly good balance. When you're good, you're Great, and when you're in trouble, g'luck you'll need it.
As for Clerics-
Now that our campaign restarted I'm up to 2nd level as a Cleric of St. Cuthbert. (ps- survived level 1- woot!)
-Frankly, right now I have no problem healing people. This may change as I level, but for now, while the fighters are writing down their kill counts, I write down exactly how much healing I've given each of them. Turns out in the first session of the campaign I basically healed both the fighters' hitpoint totals twice over.
-They profess they're love for my cleric with this. Ok, so it's connect to the top, but my Wizard NEVER really garnered thanks for anything he did. On the whole, I find that party spirits are simply higher for the cleric being there.
-Clerics, like Wizzies, can research- so really they're just as capable of questing for power as Wizards. The only difference is that many clerics will avoid the whole pride thing, and keep they're spells within their ranks. If I make anything, I doubt I'll tack my name on it / gain fame for it.
-Being a whipping boy / little pawn or peon in a big big church can somewhat stomp out the whole "I wish to gain POWER, MONEY, FAME, and GODHOOD!!" line of typical adventurer thought.
-To counter this however, isn't that line getting a little old anyway?
-The heavy armor and ability to fight somewhat well (especially with a few cleric spells like Righteous Might etc) means that a cleric can wade into combat if spells are not needed, not effective, or not available.. Usually if this happened to my wiz I moved directly to "Totally useless and trying to survive" mode.
-While your spells are not as flashy, if you take the support role your actions can have just as much effect- especially if your enemies are really resistant to direct magical attacks. If I'm about to cast Heal on the party Fighter, neither he nor I will care if the monster has SR or high saves.
-And for Roleplay purposes, while i can't stare down entire patrols or float down into their midst (more like trudge through in heavy armor... hm maybe one day with lots of luck ^_^ ), I get to do other fun things- like preach! Call others dirty heathens! Okay, that's more my paladin friend's line.. but still. Being in a church or using religion is a great thing to keep you motivated as a character and active in the game... unlike poor wizards ("I go lock myself in my tavern room- smack the wall with the bottom tip of my wizard's staff until the couple upstairs stops the screaming match, and then proceed to research/brew a potion" *and the player gets a sandwich while the others roleplay and explore the town*).
On the whole, I can easily have fun in either setup... on paper, a wizard MAY look like he's got far more power (although my cleric has the potential to cast Destruction, Disintegrate, Slay Living, Harm, etc etc etc), ultimately lining the two up and going over the numbers is pointless if you're trying to figure out which is best for a party. Both have their own purpose in a party, and these purposes do not match up so perfectly as to make one a certain choice over another.