I like 120rnd midcaps, but maybe thats because that all I can get for my PTW...
I hate STAR mags. I could never get more than 31-32rnds in em meaning the 3 that my hopup eats reduces me to 28-29rnd mags, less than a real mag. Also I find that my STAR mags would jam so often they where useless, often every other mag would jam half way through even when lubed.
When using normal AEG's I was always an advocate of lowcaps, 50-80rnd mags. Just personal opinion, don't really outright hate other mag types.