The Ergo has been my daily for few years now, and some iteration of Logitech's style of thumb ball since about 2004, I'll never go back!
I asked though because i was curious to have a point of reference for looking at the differences. What do you like about the Huge?
Oh! I feel like I'd cramp up with an index mouse, but that's neat!
I love my Ergo, honestly. The programmable buttons are really nice, and i like the horizonal scroll wheel leaning. Plus the angle is a lot more comfortable than their other ball mice.
What's really made a difference for me though is the precision mode button. It's upped my graphic design game in a major way! It honestly feels kind of like having a half-assed tablet as far as the more precise control goes! It's waaay easier to draw with, though if i were doing more freehand stuff (and could draw for shit) obviously a tablet would be better.