A friend recommended the one they sell at REI. Basically any bike that's not wood. We got a Giant brand and like it so far (it's a Christmas gift). Very light
We have a Strider as well. It seems to be well made. However, our boys don't care for it much. They both know how to pedal and strongly prefer pedaling to "striding." It is good for balance training, though. For us, it would have been a great option if they hadn't tried pedal bikes (or trikes) yet.