For ages 9 or 10
Ages 9 and 10 are fully capable of driving a mid size kart. These ages will fit into a mini go kart fine, and you may want to go that way if your child is small or inexperienced. But most 9 to 10 year olds will want more speed than the mini offers. If you decide on a mid size kart, you basically need to decide which features you want.
The Mid XRS is the base model. It is the simplest version of a go kart. No electrical components.
The Mid XRX is the premium model kart with electric start, bucket seats, 5 point harness, lights and more.
The Mid XRX-R adds reverse- with forward-neutral-reverse shifting.
The Blazer 200R is the exact kart of the Mid XRX-R plus larger rear fender, colorful seats, and a plastic hood.