i shifted from chesskid to chess.com when my rating was about 1300
When to move to chess.com from ChessKid?

At the rating level you mention, everyone blunders in every game. When your brother learns to analyze and spot his own mistakes, he will see the errors of his opponents. When he consistently beats players below 1200, it may be time to play in a larger pool.

Ziryab yes my Dad can download games but i like how in chess.com you can use self analysis right after you play and make trial moves and see the evaluation. But maybe we can do the download for now. I know sometimes people say not nice things in the chat when they play me, even if they know I am a kid.

If you are a child, you should turn off chat. There's no reason to be subjected to abuse from "adults" who never matured.
Computer analysis cultivates laziness.
I coach children. My advice: analyze with a stronger player over a physical chess board. You will learn faster and the lessons will stay with you longer.
One problem with computer analysis is that it makes you more aware of small differences in the quality of certain moves. These small differences are vital when you are playing master level opponents. They are mostly distractions for players below 1600. Between 1600 and 2200, they are sort of a gray area--sometimes helpful, but often not.
My little brother (Kindergarten) is about 1000 chesskid, 800 USCF. Chesskid is better for his age, and also has better lessons and videos for him. But it has 2 big problems. First, he plays kids who have ratings all over, from 800 - 1200. - he cannot get a reliable good game at his level. Second, there are no analysis functions like in chess.com, so he cannot review his games (on his own or with me or my Dad) as well.
I feel like he should do chess.com for games, but chesskid for training. What do people think? Thank you.