I'd get both if you can spare the slots (speed+fitness+fighting+medicine pools all in all). If I had to recommend just one I'd say that's up to your playstyle. If you like herding up *recommended*, I'd go medicine. If you just like to charge in on every mob, I'd go fighting. It also depends on if you play with a regular team, and their ATs and powersets (always playing with an empath? go fighting; tagging with a bubbler? you prolly wouldnt need any, but out of those two, go medicine)
Well i normally try to team with at least two trollers or one troller and a defender, but i prefer just jumping in to herding lol 
tnx for the reply
I would just take the fighting pool. I personally have never been in a situation on my L50 WP tank in which I've thought the medicine pool would be of any use.
I am currently playing a WP/Fire tanker, and im not sure waht would be more useful, aid self or tough/weave. I normally play in a team of at least 4 or 5.