Tough choice. It’s gonna depend on the look you’re going for. Both bikes have pro and cons.
The 310 is roomier, and is just as flickable as the svart.
Built quality is on par if not better on the BMW. Reliability wise, the svart’s platform is already proven. Coming from the 390 platform, all the heat issues have been ironed out.
The svart’s engine is punchier and doesn’t need to be revved out to get something out of it. That’s a big plus for me.
Big cons about the 310GS, It’ll always be looked as the “baby GS” and not full fledge motorcycle in its own right.