The GTF Limo is simply too long to be effective--you have enemies from all sides taking shots at your excessive size. It's really horrible--no matter the direction, even if you change speeds, quite a few shots are bound to hit you while you are turning. The simple fact is the Limo is too long and not tough enough to be effective. There are quite a few larger ships that work better--the Ursa tops the list as largest but I find it is also one of the most-survivable, due to the top-mounted turret. In a Limo, I can't bring firepower to bear on a target--in a Ursa, I have a turret blasting you to shreds while I keep you above me.
The Turkey is a monster of a fighter--it's better then a Herc2 in basically every way. It's not much bigger, much tougher, and has much more firepower. If not for the final missions justifying it, I'd say it's way overpowered as a fighter.