Hi there I'm Chris the writer of Starblazer, I'll try to answer what i can for you.
Starblazer was written to be a tool kit with lots of stuff for people to chop and change, bits they can use or not, and plenty of tools for sci-fi games.
so you've got a chapter on alien or mutant powers, how to build 4 types of massive creatures or war machines, how to build starships like characters, how to run organisations like pirate groups or whole star empires like characters and have short bloody fleet battles that are fun, not bogged down in dice rolls, two sci-fi plot generators, a planet generator, over a 100 planets described for use in any campaign, three broad settings to dump those planets and plots in to, etc etc.
Starblazer is more gritty than Spirit of the century - introducing equipment - weapons, gear, armour, shields and how to buy them and the next supplement 'The Planet Killers' introduces even more equipment options flavoured for the 2nd Thermal Wars setting plus new alien style gear.
If you're looking for something more gritty - towards the Traveller end of things then have a look at Diaspora which is a new release - they're got a lot of playtests and sample rules online.
Of course you get the Fate rules with Starblazer as a bonus from your perspective and i think it gives you a whole meal deal to work with.
If you want to save money though just pull out ideas for powers from the Fate Yahoo community and work with the Fate
SRD - that's all free!
hope that helps, feel free to ask any more questions