Well, the XR is a thumper, and the DS is two strroke. i have a DS just because it was the only smoker with a 27" seat height. My son was the same age when he started riding, and I wanted him to have a true clutch bike. He grew out of it in a year. Now he rides a TTR 125L Both are good bikes, and I think the seat height on the XR was lower at the time, so we went with the DS
I ended up getting a PW80. My son loves it, he has very good control over it right away and we did some really cool trails on the first day. I would have never trusted the beater Z50 he had to go that far into the bush. He will outgrow the PW80 within a year or two but his 4.5 year old brother will be ready for it by then hopefully.
