the cobalt and disciple are both up there as 'the best light frigate'
the cobalt is robust and reliable (as far as light frigates being reliable goes)
the disciple is a nice little cheap spammy unit with a good support ability.
the skirmisher falls behind simply because it isnt cost effective (until you get late game Vasari research, but this is the case with all vasari frigates/crusiers). And for early game cost effective is life or death.
In the end however, all light frigates pretty much do the same thing and are balanced well.
