choosing a classFollow

I can only say this because I've tanked a few things as a protection paladin (not raids, but I've tanked enough instances to know the most basic of basics of paladin tanking) and then if you look at my sig you'll see that I've recently created a warrior which is my next project to level up, and honestly if you want to get a real feel for what it feels like being a tank, go warrior. Paladin tanking, to me anyway, feels more like a hyper-grinding; just the mobs happen to be in an instance instead of out in the world. You really don't have to do anything special about tanking that you wouldn't do while AoE grinding, but warrior tanking as I'm beginning to find out, is a lot harder than it looks. I think that by leveling a warrior, I'll get a better feel for how the MT is having to play in a raid and maybe I can anticipate what he will do a bit.

Well, as you stated, Pally tanks can hold aggro on more mobs. Warriors can only really hold aggro on 4 mobs (i.e. Thunderclap) - any more, and it is much harder.

However, warriors have a ton of single-target threat generating abilities. That is why they are preferred as MT in end game raids. They can grab onto a boss, and make it impossible for anyone else to pull aggro.

As to which one you want to pick is completely up to you. I would recommend making one of each, and having fun with them. They are COMPLETELY different play styles.

My recommendation - if you want a hardcore raiding Main Tank - roll a warrior. If you want to have fun in 5-mans, and pull silly amounts of mobs together while the mage AOEs, roll a Pally.

I am a Prot Paladin, but I would say to get the best feel for tanking, roll Warrior. They were tailor made for the role and originally the only tanks taken seriously (at least from Paly's perspective, for good reason).