Definitely a balance bike. The Islabikes Rothan is great- a little more expensive but really well made and has a rear brake which functions well with little hands and pneumatic tyres which many others don't.
Our eldest was a little slow getting to grips with the balance bike (over 3) but he's a little caitious andI think he'd never had the right location. Camping early this year on a gentle grass slope he suddenly cracked it.
He got an Islabikes Cnoc 16 pedal bike for Christmas (he's 4 now). Mrs M insisted we got the stabilisers as well in case he didn't manage. First try on my Brother's sloping drive he manages a few short runs without being pushed. Today we went to the park- he got on and rode away. My proudest Dad moment!
Going Solo
I think in summary, the hard cycling skill to learn is balancing, not pedalling.