The 710 Axis is measurably larger and has a recurved blade which some find more difficult to sharpen since it can't be laid flat on a benchstone (mine does just fine on a Spyderco sharpmaker). As well, it has G10 handle scales which meet the stainless liners evenly at the edges. The 720 Axis doesn't have the recurved blade and has aluminum scales which cover the stainless liners. Another difference is that the clip on the 710 is positioned for tip-up carry in the pocket, and can be changed to the left side making for an ambi knife altogether; the 720 is designed for tip-down carry, and can't be changed to the other side as there are no predrilled and tapped screw holes standard. The 720 is a smaller, more pocketable size (by about a half inch closed and an inch open I'm estimating from the catalog) and has a more contoured grip to protect the fingers when in use. Though it all depends on your preferences and uses, I'd recommend the 710 over the 720 since I've found G10 to be more durable and certainly more scratch-resistent than aluminum. That's a small detail, however, and I'd judge by either the pictures or by going to a cutlery purveyor and trying both out to determine which one you'd like better.
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Professor
Ever notice no other candy tastes quite like Pez? Oh yeah, and the BM Axis rules.
