What sort of bike for 3yo?

[muttleydosomething]

We live in inner city, no garden, but there is some paved space at the end of the street for the children to play games. My 3yo son loves his micro scooter, which he has been using for a year, but I note with anxiety that all his peers have balance bikes (but don't share them around, as they're always used under parental supervision, and our time is golden). We don't really want to buy a balance bike unless it has real benefit as we don't have much to spend, and it would mean not getting him a real bike until much later. Any pearls of wisdom, anyone?

The principle of learning on a balance bike is definitely the way to go, but at three I would spend the money on a small, light pedal bike and take the cranks and pedals off to start with (bike shop will do this for you if necessary) until he has the hang of balancing.
I watched my 3 yr old cycle off into the sunset today with 10 mins tuition after a year on a balance bike, his smile of achievement was priceless.
We have islabikes which are brilliant but expensive, worth looking on eBay for secondhand ones ( Cnoc14 for a 3 yr old) other threads have mentioned Frog bikes as being good. Don't buy some heavy steel thing from Halford's or similar, it will be difficult and unpleasant to ride.
Don't be tempted by stabilisers, they teach the child not to balance and to go slowly, and then it's difficult to get rid of them. Ds1 was riding a bike years before his peers, it's nice to see so many little ones on balance bikes now

2 wheel scooter with big wheels (6-8" diameter). Balance bikes are over-rated and they can learn a lot about balance from the scooter.