Actually all LF are weak late game except for the vasari ones. With the armor uprades and the self heal they actually are quite resilient, even against lrms. They also do good damage, depending on the faction(I forget, is it the vas loyalists who get more damage from pulse weaps late game?)
I was talking about just the abilities, but even as a whole I think the Advent disciples are better and here's my thinking...
LFs play a very niche role...going off of the two roles I established earlier, I think the disciple is the clear winner in the first role (countering flak early game)...at this stage, you aren't going to have a lot of weapons technology, and going just by base stats disciples are definitely superior to cobalts or skirmishers...
However, even in the late game I'd argue disciples are better...the only good role for LFs at this point is to deal with kiting LC fleets (I mean, in theory someone could burn 1000 fleet supply on just flak but I'm thinking typical/realistic situations)...in this case, firepower (and the ability to kill the carriers ASAP) is preferable to survivability since this isn't a true fleet engagement...disciples have a better base DPS than skirmishers and have +30% bonus via techs for both Advent factions....additionally, they are more economical than skirmishers (though Vasari probably have a better economy so that may be a wash)...
Finally, that disciples can also use their awesome ability on carriers I just think overall makes these things the best LF in the game at any stage...