My 2 kids had never a motorbike before last summer, so they are noobs for sure. We got my girl (age 8) and Honda 50 that is physically too small for her, but it has built a lot of confidence because she can easily reach the ground and is strong enough to pick it up when it tips over. My boy (just turned 11) is on a Honda 70 and it is a similar story. The bikes physically are too small, but fit them very well with their ability level.
A friend has the PW series of bikes and I have to admit that I would probably pick the PW series over the Honda series, but at that level they are both very similar.
My kids have loved their bikes. We get them out much more often than we have the jeep. The bike, the noise, the speed, the bumps, the hills have all been very intimidating for them, but each time we go out they get more confident and their skills increase. I have just taken the approach with my kids that they never have to do anything they don't feel comfortable with, and I have often had to walk my girls bike down a hill because she was confident to go up hill, but still scared to look down the long hill. So the next time out I find a smaller hill and she masters that and eventually we have mastered the hills that scared her before. I am very happy with my choice to get my kids started with motorbikes. I can't wait for my boy to get 14-15 and have him be able to hang out with me on off-road adventures.