I just posted in the Unholy > Blood post, you can check there for my builds and rotations. I haven't used frost so I can't tell you what Unholy is better at, but I can tell you that with 3 diseases running on the main kill, popping pestilence, blood boil, then unholy blight, I never have a problem with adds running off.
I usually Strangulate a caster, then DG the other (if more than 2 I'll have someone else CC/DG it. If I can I'll just run right into them and use my normal abilities if there is no possibility of pulling adds.
I love Unholy tanking because I get great AoE aggro on all the mobs almost immediately and also do insane dps at the same time.
My endgame proposed build will be much stronger against casters with the anti-magic bubble and stronger against melee with more avoidance talents. I am leveling with more of a DPS build at the moment to get to 80 easier, but at 80 will be well able to tank near anything.
I am 2-handed tanking/dpsing and recommend that to everyone. Never, ever, ever tank with 1 handed weapons. Your miss and parry rate skyrocket. You will take way more damage and put out way less threat. I had a friend yesterday do a few group quests with me just for fun and she was DW'ing two of those footman swords. Her miss rate was 24%. Mine was 1.5%. That's a Huuuuge difference. Plus so many of our abilities are dependent on weapon damage that it just makes sense to me to 2-hand it.
Anyhow, my biggest recommendation to you is to try out both of them. Find a good group (guildies preferred) and try each spec out. See how it works for you. They both work, it's what makes it fun to you that really matters.
Have fun and good luck!
Edited for sig...
Edited, Nov 24th 2008 9:10am by Galenmoon