I got one of each with two starters and just picked up a second b-wing as I mainly play rebels. I'm not big on tie swarms, and don like the 'fragile' no shield idea, but I also just preordered the aces pack which is released next week

. I also will be getting the large ship packs when they are released.
But for you, if you can only afford one set then......
A. If you want a more durable ship choice then field rebels. Fewer ships too so less $$$$
B. if you want more ships which you don mind them blowing up but like to outnumber your opponent then go imperial
C. If you want to be a sell sword then buy multiple firesprays and start your own bounty hunter alliance
D. If you are a business man buy multiple falcons and rule the galaxy through economic means (smuggling)
E. if all these sound fun then sell a kidney/ wife/ first born