I rode both the 29 and 650b (medium for both) back to back at a demo day at Dalby the other day. I haven’t ridden an orange 5 before though, so can’t compare to the 26″ -sorry!
The 29 was heavy and felt unresponsive in tight stuff, until you really threw your weight at it. Once you got the hang of riding like that it was good, but I suspect for unfit people like me it would be very wearing over a longish ride. The 650b was like a different bike – it was lighter for a start, but could make the corners without leaning on the bars like a gorilla, and climbed way better. If I had the money I would be very very tempted…