That KTM 350 makes me salivate!
I still think I'd take the Gas Gas 250f over the straight Yamaha. The suspension can be tweaked, the engine super easy to dial. The Yamaha chassis can never be made to feel like a Gas Gas. Not that it's bad, it's a great bike, it just doesn't have the USB cable connection to the brain that the Gas Gas has.
It's still a four stroke.