Don't compromise. You'll be happier. Get a bike that is as close as what you feel is optimum off-road as you can. If you need something that can be ridden on the street then get one that you can license where you live, but don't take into account its street capabilities. All else being equal (suspension, traction, power delivery), it is light weight that will help you starting out, and even after you get some skill. Not all small displacement bikes are lighter than larger displacement bikes either, so check the specs when doing the comparison. But back to compromise - I've had a 'dual sport' (DR350) and I've had a *big* adventure bike (R100GS). Both were compromises. Of course the DR was capable off-road, but it was also a bit heavy for the dirt. The BMW was a big pig off-road and didn't handle all that well on the road. After going down the compromise road I decided to not compromise anymore. My Husaberg is a great dirt bike and not well suited for the street (although with street tires/wheels it would make a great SM bike). My Ducati is a fun sport touring machine and sucks on rough gravel roads, I imagine it would be a nightmare on a trail with street tires. Why compromise? Get a light dirt bike and only ride it in the dirt. Ride your street bike on the street. You will be happier. I am.