Right now it doesn't really matter at all, but in general:

Bigger pools (with tons of workers) will find blocks faster but you'll have to share those blocks with [thousands of] other workers. Tiny pools with less workers won't find blocks nearly as fast, but if/when they find one, you get more of a reward because you don't have to share it with as many people.

So personally I think it's best to find a sweet spot in between... one with a high hash rate but low-ish number of miners. But again there are only like 3-4 pools right now so pick whichever you want!

Strut on!