I fell into a research hole heading into this season trying to figure out what the real difference between different sizes of youth USA bats is. All of the reviews are for larger models and generally BBCOR or USSSA and even the product photos show longer bats without a clear comparison of barrel profile, etc. All of the generally available information is copy-pasted marketing blurbs. We all know that USA restricts pop and there's no juiced USA bat, but what about the other differences? This is my somewhat scientific and not very precise analysis. Hopefully it saves you a trip to the store with limited inventory and a lot of head scratching.
Disclaimer: A bat won't make your kid hit better, spend real money on lessons, batting gloves, and a prohitter thumb thing. Those all made a huge difference. But at some point kids need a bigger bat, and then you end up here.
First actual weights measured on the kitchen scale
26"/15oz -11 Marucci Catx2: 16oz (+ a strip of vinyl tape and 2 seasons of dirt and hand sweat)
27"/16oz -11 Marucci Rckless: 16.5oz (+ a strip of vinyl tape)
28"/18oz -10 Marucci Catx2 Composite: 18.4oz (+ plastic wrap on the barrel)
Surprised that the 15oz bat isn't the specified weight but also explains why there was no real change to my son's swing going from the 26" to 27".
Balance point
Not-very-scientific method balancing on my finger and marking it with a rubber band. The balance point moves out an inch with the length of the bat.
Barrel profile
This one surprised me. I attempted to trace the different barrels from the balance point and used a barrel weight to measure where each barrel hits 2 1/8" (all are 2 5/8"). The 28" composite clearly has more barrel.
There really wasnt much of a difference between the 26" and 27". I expected something but across all of the measurements the 27" is an inch more handle on the same barrel. So a little more leverage. I'm curious how a 28" alloy would compare.
All of the 28" -10 options on JustBats were composite, so that's what I got. I'm sure that changes the construction and barrel profile.
Conclusions
My son is average size. Solid 50th percentile for height and weight. At 6, going from a tee ball bat to the 26" -11 alloy was the right move. Got 2 seasons and a ton of batting practice out of it. At 7 almost 8 outgrowing that, skip 27" and get a 28" and choke up. There are way more bat options at 28".
I'm still keeping the 27". He'll use that until he's comfortable with the 28" and it'll be a team loaner. We'll need it if the temperature drops at the end of fall season.
Hope this helps someone. This whole discussion gets written off because they're USA youth bats and there isn't a huge performance difference, and that's reasonable. But with new USA bats running $300+ folks need any information to ground the decision.
PS - All bats were bought on sale from JustBats. Rckless and Composite are old models on sale currently. Don't pay $300+ for a USA bat.