More wattage allows you to fire some of the newer sub-ohm tanks that now have up to 4 coils in them (Smok makes one, a TFV4 that I believe they recommend starting at 75 watts

). TC mods can also be used as VW (Variable wattage) mods. Most of the better mods now come TC equipped. What you need to ask yourself is do you want a single 18650 mod or a duel 18650 mod?
Single 18650
Sig 75 TC, IPV D2 are very popular.
Pros: Smaller, generally less expensive
Cons Shorter Battery Life between recharges, limited to about 75 watts
Dual 18650
IPV3 Li, IPV4S, Sig 150TC, Snow Wolf 200 are all very popular
Pros: Longer battery life, up to 200 watts
Cons: Bigger, generally more expensive
These are not by any means all inclusive lists, just the ones that come off the top of my head that I think you would like. You should be able to find all of these online for under $100
Personally I really like the IPV3 Li. 200 watts (after the upgrade), supports both Ni200 and Ti01 in TC, built very sturdy and feels good/solid in my hand. Good luck!
Cheer
Steve