So I am the main tank for my guild, and we have been doing Kara for several months now. The biggest problem is that none of the drops have been tank gear! Well, except the bracer from Attuman the Huntsman, and the belt from Moroes. So while the rest of my guild has gotten tons of upgrades, I am sitting at a mix of heroic and BS gear.
We have gone through enough times for me to get enough badges to pick up the [item]Girdle of the Fearless[/item] as my first badge piece, and now I am back up to 100 badges again, and still no upgrades!
Now we are moving onto ZA, with Kara on farm, and I am the weak link! I have managed to tank the bear and eagle boss, but I feel like I am straining the Healers ability to keep me up.
They're both huge upgrades, and IMO the threat stats on the legs make them a bigger upgrade over the Kara legs than the chest is (I got the chest first because Wrynn did drop for me and Panzar'thar did not, but if I'd had both, or niether, the legs would have been my first piece).
Get the legs. Why? Because the S2 chest is good for tanking and you can have it tomorrow.
[item]Merciless Gladiator's Plate Chestpiece[/item] vs [item]Panzar'thar Breastplate[/item]: Glad has much better threat and better effective health. The only thing you lose is some defense, replacing it with the inferior resilience statistic. I'd wear the glad chest over the panzar'thar because of its superior threat gen. Yes, [item]Chestplate of Stoicism[/item] is better than the S2 chest, but the difference is not in the same ballpark as for instance the S2 legs to the badge legs. In other words, here are your real upgrade choices:
[item]Chestplate of Stoicism[/item] vs [item]Merciless Gladiator's Plate Chestpiece[/item]
[item]Sunguard Legplates[/item] vs [item]Merciless Gladiator's Plate Legguards[/item]
See how much closer the stoicism is to the glad?
Survivability is not your issue right now. The gear available from honor and badges so outgears T4 that it should be very hard for you to die. The real challenge is keeping apace of the similarly badged-out dps.
Go legs! Especially in ZA, there are going to be a ton of dps races to down bosses, especially if your raid is going for timed chests. You need all the threat you can get. I do not even worry about avoidance in there as much, I throw on shard of contempt and eat hit food to get as much aggro as I can, so I don't get some warlock getting 1 shotted when I am not looking. Badge chest is nice, but it is not even close to legs.