BK400, you find someone who has broken a 710 - or a Para - you let me know, OK? You can snap the tip on either, but breaking them at the pivot?
Scott, to me the question between a Para and a 710 is pretty simple - which do you want, a 3" folder or a 4"?
I'd go for the 710 (my big EDC is actually a 730), but my 3" EDC is a Yojimbo.
Leaving aside the BM vs Spydie pissing match, I have always thought that in the various matchups, Spyderco's strength was usually in the smaller pieces, and Benchmade's in the bigger. You've narrowed it down to perhaps Spyderco's best medium-small piece and one of Benchmade's best medium-bigs - which size do you want or need more? Does tip up/down make a real difference? Do you want a recurve, or hate to sharpen them? While they're both great knives, they're NOT very similar to each other - which one suits you better?
I do think, as a steel snob, that the M2 option on the BM is a serious leg up. But your real decision point probably should be on feel in your hands - have you handled them both? If you haven't, I'm guessing doing so will point you one way or the other.