It ultimately dwells down to these two as the most "useful" professions, physicists, miners, sabotuers and governors aren't all that popular.

Which one would be more useful in all aspects of gameplay? kinda thinking..some rival players are catching up and i'm contemplating a profession change.

For individual play: excavator. It provides more artifacts which gives you more att/def/res/hull/shield/energy

For a more legion oriented play: Fixer helps with defending bases, planets helps with fighting everything.