If I were to take over a world filled with biological life forms my first ship to engage would have scientists/biologists who could engineer a virus to kill the majority of the inhabitants.
Forget all this battle stuff. Inject the virus into the atmosphere, wait a few weeks, and then claim the prize.
Hopefully by the time they get here OUR scientists/biologists will have a way to fight viruses...
And while our scientists are working on it, how about phasers and photon torpedoes. Definitely photon torpedoes...
Never could understand Star Trek - they'd fire all the phasers and such and finally use the photon torpedoes and I was like - why didn't you use them first???