ah i see - no worries for the advice.
defenses are extremely easy to research. personally, i like building defense-heavy ships, especially if i'm playing as the Krynn (+50% defense). however, for them to work you do need at least mid-range weapons. it'd be one thing if their ships had no defenses at all, but once they've got more than a point or two in the primary category (or 9 points or so in an off-type category), it pays off more to have more than entry-level weapons IMO.
i almost never start out researching mass drivers. their first two generations are very poor weapons. it takes more to research them, and you get way less in return compared to missiles or beams. though you can get up to singularity driver IV or V or whatever it is to get nano rippers, which are fairly powerful early weapons. but you'll have to pay a lot for them, so putting them on small-hulled ships isn't the best way to spend your money IMO.
beams are easy to research, and if you play evil, it's very easy to get to psionic beams, which are very powerful considering how quickly you can reach them. i almost always start off by researching missiles, though. it's just a numbers game. i typically try to have a strong enough military so that no one wants to declare war on me. i research up to stinger III or IV, and then put a bunch of them on a cargo hull -- what many players call 'paper tigers'. these things are cheap to build, and deter the AIs from wanting to go to war with you. with ships like that, i can usually hold them off for long enough to research the military technologies i really need to win -- bigger hulls, more miniaturization, logistics, engines, defenses and weapons -- not to mention the industrial and economic technologies i need to sustain such ships. in general, if you just focus too much on any one single technology, you're not going to do so well i think.