gotta assume they gutted Pegasus right down to the superstructure before taking it into battle. Absolute minimum crew, no supplies, no vipers, only the raptors needed for evac. Why they trashed Pegasus but kept Galactica only makes sense in the context of the name of the show, bad military decision.
Also, doesn't make much sense that Galactica is THAT hurting for people afterwards. She's now got 2 crew complements. Even if you assume that a good chunk died or was left behind on NC, there was still enough to operate it, plus more Viper pilots than Galactica had. Also their full set of grease monkeys, of which Galactica seems to be in very short supply of shortly after the 2nd exodus. They double up, and still seem to have less than they started with...
Actually... you WOULD be right, but it made more sense to get rid of Pegasus, because Galactica had already take such a big pounding by the time Lee came in, that Galactica simply would not have survived long enough for an evac operation.