I have both and like both. The 710 feels more comfortable and 806D2 feels more secure. If you don't have a Sharpmaker, the 806D2 is easier to sharpen on a flat stone because it doesn't have a recurve. If you have a Sharpmaker, the 710 is easier to sharpen because its blade is made out of 154CM (instead of D2 as on the 806D2). The 806D2 is safer and a hair better at piercing and the 710 is more comfortable and a hair better at slicing. The 710HS, with its M2 blade, is harder to sharpen on a stone or in a Sharpmaker than the 806D2 due to both the recurve and the M2 steel. Of course, with the M2 steel, you can sharpen the blade down to a narrower bevel, with less risk of chipping, than the 154CM base model and it will retain its edge longer. My 806D2 came with the best fit and finish of any Benchmade I've owned with the 710HS being a close second (slight lateral blade play and a rattly stop pin add character!).
My favorite is the 710HS and my "I know you're going to like this one" suggestion is the 806D2. The 806D2 was best out-of-box, has a very good steel for a blade of its size, doesn't require special equipment to sharpen its edge, has a very safe handle (by safe, I mean, hand isn't up on the blade during unexpected stops), and has enough handle and belly to handle most any folding knife task (not that the 710 doesn't also have that).