Why choose a balance bike vs a bike with training wheels?
A balance bike simplifies the most crucial part of learning to ride, which is balancing on two wheels. By getting rid of the drivetrain and allowing a first time rider to simply push their way around without anything in the way.
As the rider progresses, their stride becomes bigger, with more time between steps, eventually balancing with their feet off the ground as long as they feel comfortable until they naturally feel like taking another step to either gain speed, or slow down.
When it's time to move to a pedal bike, the riders' time on a balance bike has allowed them to feel confident balancing on two wheels, so the next effort is focusing on learning how to pedal.
All this equates to more fun riding experience, at a younger age!