I can speak a little bit to the differences between CH3 and Gauntlet 3 - we had a 2010 CH3 and replaced it with 2 Gauntlets - 12C and 18C. Most things are the same. They reduced the monitor size (for the smaller color count presses - our 18C has the same size screen as the CH3 did - it does stick out 6-8" too far imo though), index motor is a tiny bit smaller, and that's about it. Damn near the same press. It was just to keep the CH3 as the bigger presses - larger footprint, can take bigger screens and are priced higher of course, and now the Gauntlet 3 takes over the CH3 '55' smaller model.
A change they made within the past few years is they use smaller air lines running to the chopper cylinders, screen drop cylinders, which makes the press a bit quieter and smoother. This is on any new CH3/Gauntlet 3 though - just pointing it out. The only downside is the squeegee takes a tiny bit longer to completely come in contact and up to pressure so I had to increase the delay to start squeegee movement to make sure it prints the top of images. This is mostly an issue when using only 20-25psi - printing sleeves for instance.