I own both a flash ii and a mini grip. Both are excellent folders that many consider benchmarks in the knife world. Usually youd pay more for the benchmade, but go on knifeworks.com who is having a special on benchmades, you can get a full size grip for $68-80, which is around the same price as the others. If it was me Id go with the benchmade. Alittle bit better quality, made in the USA, the 154cm blade steel is better then the aus8 imo, and there is zero blade play and the axis lockup is solid. Benchmades axis lock is one of the best in the buisness. Sog has their assisted opening arc lock but it seems blade play depends on what you get. My flash has alittle up and down, but that i believe is the nature of the arc lock. Wouldnt spring open if it was tight. My flash i has non, but the lock is alittle different. Again my vote is the grip, but id eventually own the flash ii anyway lol. Not to make your decision more difficult but check out spyderco. Not everyone likes the thumb hole at first but once youget them in your hand and start using them you fall in love. Spyderco makes top quality kives and their ergonomics are some of the best out there.
Love my SOG flash II. Lightweight, holds a good edge and the deep pocket carry clip makes it more concealable.
I glued the safety lock on mine, I know some people say its crazy, but when I want it to open I want it now. I did not like to have to slide the safety then open it. One handed opening is fast and smooth.