As ex-vstrom owner the difference in weight btw DL650 and R1200GS is minimal, and GS would actually feel lighter as it has lower center of gravity. 650 Vstrom is cheaper to get but it will definitely need stiffer shock spring to handle 2up.. this is from personal experience and our 2up total touring weight was about 360lbs. Also front brake is fine for solo but was a liability 2up. Engine is a gem and tank range is sufficiently good.