I've run both, the Mephisto is an Xtra long stroke and does have a little more bottom end torque which is good if the track surface has good bite.
and it is thirsty, not the best fuel mileage.

The Mito is a little friendlier on the throttle and has good mid-range and top end. I also really like the Mito 35 WC. Sorta feels in-between both. Keep in mind, I ran all of the above stock out of the box, did no mods. All were ran on 25% nitro, 6% castor, 3% synthetic oil. Nova conical medium header, Nova 2015 pipe w/stock cone hole sizing. Head clearance was .07mm