Pro's to moving 'down a level'
More batting time
More bowling time
more confidence in himself
Con's
Ego - Having seen it more in football than cricket kids that are the 'top dog' tend to have massive ego's, then when they come up against people they can't easily beat they just give up or get all moody about things
Moving to another club to be top dog means some other player gets less cricket time so it's swings and round a bouts
ALthough playing more will help I am personally a believer in you only really improve against similar quality or better. So if it's 'too easy' then he'll not actually improve that much and again, when he bowls against a good batsmen will get hit and be devoid of ideas. Batting wise he'll suddenly not have all the crap to hit and will end up slogging and gettnig out.
Just my opinion. I'd personally keep him where he is and just do loads of training to keep him sharp and improving. THen when he gets a go he can prove himself etc.