While you're waiting for numbers . . I ended up with the GC1715 . . . and a number of people were saying it was a waste of the extra money for the higher level 15 vs the 05. I believe the EXACT same dufference are in the 20 vs 10.
I'll just share with you that the higher models in the gc lineup give you more than a $ 1200 or $1300 perceived difference.
The gc1720 seat has both a coil support AND a spring suspension which is more confortsble on bumps and smoothness. In addition they look similar is color and "general" shape but their support and width are different. In other words . seats are a bug difference.
Extra work light is nice for pre wiring purposes but not a big deal.
Engine differences are a couple horse power and really shows up in power at the higher rpms.
Any way I could get you to take a picture of the spring suspension? Does it has adjustable preload? If no pic - can you elaborate a little on how it works? I am assuming that the entire seat "bounces" up and down over bumps basically like an air ride seat in a truck or a tractor seat on a bigger tractor..... If thats the case im def sold on a 1720 instead of 1710