While some of the in game help gives some general guidance on units that are good against turrets, I've found that there are several ships that are either very, very good or very, very bad that have no explanation.
Bad list:
Teleport Raiders: These units are beyond terrible. They will take approximately 3 days to kill a Mk 2 turret. (actually, it's more like 15 minutes but it FEELS like 3 days).
Autocannon Minipods: Not as bad as T-Raiders but pretty attrocious
Bombers: This is more of a mechanical thing. Bomber Mk 2s will be held outside of weapons range by tractor beams. Get something else to tie them up first so the bombers can actually do damage.
Good list:
Etherjets (not really spectacular, but their speed and immunity to tractors makes them useful)
Teleport Stations: A stack of Mk II Teleport Stations will destroy almost every guard post and wormhole stack up through AI progress 100+ (AI lvl 7). You'll lose 5-10 which (I think) is a pretty good trade. They also do it very, very quickly so if you're on a time budget they're by far the best choice.
I'm sure there are others if people have some to share.