I also tend to use all 3. As it usually stands, there's always someone coming at me with all their defense in only 1 or 2 techs, usually only 1, or 1 on ship type A and another on ship type B. So if my attacks are spread across all 3 areas, I'm guaranteed to be able to snuff them. That was mostly in GC3 and I haven't gotten too many battles in GC4 just yet (only just got the game and work interferes, so more time this weekend).
That said, the tech follows a general level of realism. Pretty much everyone will discover how to throw rocks at some point (kinetic - kinda general purpose, low range accurate, decent damage that sharply falls off at range), then boulders (missiles - high damage that splashes, longer range, less accurate), then learn how to dig under the walls and sneak in (beams - more precise, localized damage so "less" damage overall, but devastating to the spot targeted even as accuracy falls off with range but not damage potential).