I'm a real believer in a soybean based ration balancer as the best thing you can feed after good forage.
I fed Buckeye for years then moved to where Progressive was easier to get. I don't see a difference between the two and have heard the same nutritionist did the original formula on both. Of course when Cargill acquired Progressive, then we could no longer get it easily.
This sounds weird but about that time I noticed that Chewy.com had Buckeye Gro N Win and other things. I get my ration balancer on autoship from Chewy. I do live in pretty remote country.
If you feed over the winter (and eastern MT can dang sure have winter) enough racebred weanlings, you can really see the effects of nutrition. I'm old and I've fed a bunch of them. I tried a nationally known brand of feed that was supposed to be great stuff. Yeah, in 2 weeks my pen of big, strong, muscled up colts absolutely melted into potbellied, cow hocked, no muscled pukes.
I see a lot of difference in adult horses too, but it's really noticeable in growing horses. I don't feed anything but Buckeye. They have to have those amino acids to be healthy and that's what you get.
I also like that I don't have to feed huge quantities - more room for hay.
Dislikes? Only the price. Ya get what ya pay for.