My experience with the Sevr is they fly great but leave poor blood trails, in addition the forward angle of the blades upon entry leaves them susceptible to levering sideways if they catch a rib on the way in.
Grim reaper mechanical on the other hand fly's just as well and has been exactly the opposite for me, with great penetration, blood trails like a river. This years 6x6 bull quartered away, broke rib on entry, blew through offside shoulder, bull went 30 yards and tipped over in a lake of blood. Big bodied Wa blacktail this year took an arrow center of the chest and almost exited through rear ham next to the tail, looked like a 5 gallon bucket of blood was poured down the mountain. Everyone has a favorite but figured I'd share my experience.