I've been commuting on a DT175 for the last 2 weeks, 100kg & 6 foot 4... and it's an awesome little bike. I can do highway with it, but it prefers side roads, it Wheelies quite happily with me on it.
Off road is great, it handles rocks, mud, sand, logs, everything with ease.
I have ridden the Honda 4 stroke 125, and can honestly say there is no comparison - 4 stroke will get you there, 2 stroke will get you there with a grin.
Let me know if you need a test ride.