I do both, am I weird?
Seriously. I'm constantly busy doing sweeps and raids all over the place, sending transporters full of bombers over half the map or dragging golems and starships through one system after another to mop up threat; but at the same time I have a solid defensive grid that can take pretty much anything from Roamers to CPAs and standard-sized waves with a minimum of attention.
So myself, I can't tell whether I'm more offensive or more defensive. I definitely spend more time planning attacks than planning defences - but since I play with zero AIP over time, which allows for very long-term games, my overall rate of expansion would probably seem very defensive to most players.