One size doesn't fit all, IMO. Except for playing time. You need that.
But IMO, young kids need to be in situations that nurture their enjoyment of the game and make them want to come back year after year. For some, maybe that's a high-level team ASAP. For others, they're fine to take their time, stick with their B-level teams with teammates and coaches that they enjoy, big fish in smaller pond.
This is the hard lesson we learned this season. Moved DD from 12U "B" team to a high performing "A" team last year and by March she was ready to quit softball completely. I thought the competitive nature of the "A" team and being around motivated girls would make her want to work harder and be a better player, but it actually did the opposite - she completely melted down. Just recently settled into a 14U B level team and she is performing like she used to. And most importantly, I see big smiles from her on the field again. She is definitely "big fish, small pond". Wish we hadn't wasted half the season living out MY "A" level dreams...parenting lesson #202.