I’ve had both and sold both. Full disclosure, I am abnormally picky about my stuff and some of this analysis may be viewed as minor or trivial. That being said, I am of the belief when spending that much on a stock or chassis system that it should be about as perfect as perfect gets, and to me, neither of these stocks are worth the investment.
Regarding the JAE, I have large hands so the palm shelf basically does not allow my entire hand to be on the grip. It’s pretty uncomfortable. Not an issue for most but something to keep in mind. The cheek rest for whatever reason is “open” at the top and has some holes hard/jagged edges right where you put your face. You can cover it with foam or whatever but not exactly the type of finish I would expect from a stock of this class. The magazine adjustment takes some time to get right and you need to reset it each time you remove the BA from the chassis. Majority of the time, the mags are either tough to fit or fit too loosely. Forget about running different types at the same time. They don’t balance particularly well to begin with but add a heavy barrel contour and it feels like you’re swinging a 10 lb. weight from the muzzle. It’s also another $200+ to get them set up for ARCA/Adjustarails and after paying $1800 for the stock alone that’s just a no for me dawg. Hard pass, really don’t understand the love for them.
The MG1L I really had/have no complaints about other than cost. When you consider that you need the stock, bottom metal, plus additional investment to get it set up for ARCA compatibility, there’s just no way I can justify that when I can go buy an MPA for literally half the cost. Aside from being different and cosmetically pleasing to look at, they do not help you hit targets that you would otherwise miss. They are NICE, but they are not $1600+ nice.
I understand I’m in the minority but I’ll stick to my peasant MPAs, Manners, and ACCs.