GURPS is a MUCH broader system- can do just about anything. Not always very good. But does the job. Everything from fistfights to starships.
Storyteller is limitted to a human, or not especially above human, levels. It loses scale at right about "elephant". Including the kinds of weapons that kill elephants. Really, the world of darkness weapon system in general is pretty laughable.
But if you're planning for a stealth/paranoia/horror game. It is the better system.
I honestly haven't seen a GURPS book in stores in forever. I recommend you get online. There's nothing you can't buy a PDF of these days.