The nitrile is just ever so slightly thicker, smoother and slightly grippier. The gloves themselves fit nearly identically. As near as I can tell, the 710 and 720 are the same gloves, with the 710 getting a smoother grippier foamed nitrile surface and the 720 getting a slightly more textured nonfoamed blue nitrile surface.Do you find these are larger than the 720's? My one complaint (because I'm a man and don't care about color) is they're a little too small with a thick liner.
I use the same superlube on just about everything (except O2 stuff as noted). Zippers, seals, etc.
From the wrist back, the are absolutely identical, even the coating.
If only one or the other were available, I would be perfectly happy with either, but next time you're putting in an order to somewhere like Zoro, consider tossing in a pair of CS710 and see what you think. I like them. In both cases, I've found that going up in size doesn't make the fingers ridiculously longer, so going up a size to accommodate a thicker liner is a reasonable option. Some gloves add like a half inch to the fingers when you go up a size, and floppy fingertips are a peeve.