Which should I be going for?

Two sets, one for feral DPS and one for tanking, is a good idea.

(Assuming Feral leveling < lvl 50ish) Imho: Agi/Str. Both add to Attack power, and I've had an easier time levelling when I kill things faster, than when I can take more of a beating.

Caveat: if you plan on levelling Bear doing mostly instances with a group, then perhaps favor Agi/Sta. And from what I understand, the higher lvl you get, the more important Sta becomes.

But best of all is as AppleJax suggests and one set of gear that favors each so you have gear tailored to either situation. In my experience, there is a lot of overlap with the two sets at lower levels, and having 'two sets' mostly just means swapping out a few pieces, rather than an entire set.

Bear: Agi/Sta
Cat: Agi/Str

One reason feral levelling is so awesome is that unlike the other tank classes, druids are the ones most likely to actually be specced for tanking. Our DPS and tanking tree is the same!

While paladins and warriors can be great tanks, the likelihood one of them is levelling Prot-specced is really small. Whereas something like 90% of druids level feral. Whether they have two sets of gear, for both DPS and tanking, is another story, but it really doesn't matter too much in the early game.

Well, with this new healing gear that has added DMG. I can see more resto druids leveling balence now. Next Expansion I'll level Archiee balence where in TBC I leveled feral.

True that. Paladins can level holy now. Hell, they can DPS as holy if you need AOE for your instance.

Hehe. I guess I'm attracted to the off specs - I'm currently levelling a Prot Pally (45) and Balance Druid (26).

The pally AoE grinding/tanking is hella fun, and the Balance playstyle is quite different from Feral. Best of all, I still have cat/bear to fall back on when I need to.

It sure would be nice if moonkin form was a base skill. :p

It sure would be nice if moonkin form was a base skill. :p

Then we would be having TOO much fun.