Is there really ant reason for to have an alt character in the same faction? You are awarded a new ship at every promotion but afterwards can buy the other two. And because the majority of your time is spent in space is there any reason to create a new character to try out the other classes of ships? Do the class specific skills really have that much of an effect on your ship performance?
When you have alt-itis, you don't really need a good reason.
I have a Klingon (cuz I wanted one, not really for the PVP aspects). My federation Escort Tactical arse-kicker and I plan on making my Engineering "Scotty" nerd later. Not for better performance or uber gaming, just because it's fun.
I have noticed that class specific skills have an effect on ground combat performance, but ship performance I have no opinion on yet...until I roll my Engineer.