The DL1000 is a wonderful bike - great for two up, all-day long comfortable (at least with my gel seat) and plenty of power throughout. As far as keeping up with your mates on their sport bikes, that's up to you. Generally speaking better riders on slower bikes will be able to keep up with less skilled riders on faster bikes. YMMV. If two up is your thing, buy the Vee. If going off road is your thing, the Wee may be more your speed, but from what I understand is somewhat less happy two-up touring and for sure has less power. Decide what's important to you and try to test ride them both.
Steve
Both are great bikes, I have the 650 - if it didn't exist, I'd have got the 1000.
The 650 suits me best - mostly 1 up, enough power that the occasional pillion isn't an issue, better handling than the 1000 and better range (don't care about economy - but parts of Oz - it's nice to know you can get to the next TWO petrol stops if you have to

).
I ride off road a fair bit - the 1000 is only a bit heavier, but the weight is higher than the 650 - I'm not particularly tall or strong so the 1000 would be a handful for me off road.
Either bike can embarrass sportsbikes on the right road (rough, windy, and preferably damp

). But it's just more satisfying to be waiting for a Superduke or Speed Triple to catch up on a 650 than it is on a 1000 - so in that regard it depends how cruel you want to be

. On straight roads though, a 600 sports bike will leave you in the dust - you'll just have to be patient and pass them when they stop for fuel or a stretch

.
More seriously, if you plan to be doing more than ~140kph regularly, get the 1000. Up to about that speed there isn't much performance gap - you just have to rev the 650 harder - beyond that the 1000 disappears.
Pete