DS has a balance bike he's used all of three times...he's never been interested in his trike/ride ons, but he goes back to his friends scooter over and over.

DS hasn't shown the same interest in another friends' trike...it's a 'cheaper' one, so I'm guessing it might be heavier/harder for him to use. I think it's like comparing Gala apples with Granny Smith's!