I personally buy and use benchmade knives for my single bladed folder needs (don't have a spyderco yet, although I might eventually just to see what the fuss is about). Part of that is probably because they are much more lefty friendly, but I also really like the axis lock (I have one liner lock (cammilus heat, the knife that led me to want the 705-401 (made me decide I did have a lot of use for a smaller blade

)) and a lockback (and old gerber model, which I actually gave to my brother), but find the axis lock just much more cooler and more enjoyable

).
I bought the Rittergrip as my first high quality knife (due mostly to the people here, of course

), and found it quite a nice knife, a very good slicer with a high grind on it. I ended up selling it recently, due to the fact that I found that the tip wasn't really quite pointy enough for my tastes (mostly due to the high grind), and decided to stick with my 806d2 for heavy duty carry, and pick up a
BM 705-401 for lighter duty every day carry (including travel to states with 3" legal limits and such).
I think that for what you want, neither the 710, 806d2, or rittergrip would be a bad choice, but the best choice between those all comes down to what you think your personal preference will be. Most people think the 710 has a slightly better blade for utility then the 806d2 (no personal experience, since I haven't handled one).
Of course, there are also the people who'll suggest you to get a nice balisong (which I also enjoy), but the legality issues in most states for the carry of these makes that a bit harder (my BM42 never leaves my room

). They do have the advantage of quite possibly the strongest lock of any folder, surpassing even the great axis lock.