Use GURPS for the background info in the splat books.
Its research is pretty decent.
Don't use GURPS to play except if you fully plan on restricting yourself to the Core Rules.
This is what will happen if you don't follow this advice:
You'll spend weeks fiddling out which rules you actually want in your system, tinkering around for hours because "just taking everything from eg Martial Arts" is not an option.
Well, its a theoretical option but a single Combat sequence with full MA rules will make it such a mess focused on miniscule details that nobody will want to repeat this shit afterwards.
And going with the core rules only is really only an option if you don't want super deep rules with stuff like different targeting zones to attack.
Trying to introduce GURPS into a GRUP that doesn't consist solemly of people on the Assburger spectrum will lead to two things: Switching to a different system to play
A GM whose sole future interaction with GURPS will be creating useless character builds that will never ever see play.