I have both -- and I actually prefer the less costly Mini-grip. Why? Ergonomics.
When closed, the Mini's thumb stud has about a 1/8 inch gap between it and the frame. The 707's thumb-stud is right next to the frame. No gap. Hence, the Mini's stud is much easier for one's thumb to "find" to push the blade open quickly. This is especially important if ya ever need to use the knife in some high-stress application where you're "all thumbs." OTOH, if you have the delicate manual dexterity of a violinist or brain surgeon, then maybe the 707 will fit you just fine.
Both knives are pretty small, but the Mini is about 1/8 inch longer overall. That little 1/8 inch, along with the jimping on the Mini's underside below the lanyard hole where your little finger slides on the scales, makes a significant difference in feel... and control. The 707, however, is smooth here, with no "aid" to help your little finger. In addition, the 707 lacks a lanyard hole -- important only if you want the option to attach a lanyard (which I feel the 707 could really use to enhance control).
The ONLY knock I can make on the Mini is this: its superior "grip-ability" comes from its more sharply-defined knurling and jimping on its handle. That tends to abrade/chew up pockets and trouser waistbands (espec. if you carry IWB). For EDC carry via the IWB method, the smoother (and certainly "dressy-er") 707 will be easier to slip into the waistband under a belt (say, at the "appendix" position). The Mini-Grip won't slide in-out as smoothly.
However, once in the hand, the Mini "works" much better. Playing with both in an "eyes closed" subjective test, the Mini wins every time. Both are "bullet-proof" tough, but the Mini might be a more "perfected" design. And, it's a bargain.
I'd buy another Mini-Grip in a minute if I lost mine. Not so for the 707. YMMV.