The down side to a thumb throttle is that the thumb has a slow awkward response compared to snapping the wrist .
I put a twist throttle on a heavy weight sport quad and it's ok but it is off limits to green horns because I've seen a bad outcome more than once . Machine takes off and the last thing that goes threw their mind is to back off the throttle but instead roll into the throttle because the machine is going one way and their body the other .
Kind of like the lefty throttle , I think most snowmobiles have seen a bad outcome of one of them at least once , I have and it costed the guy a collar bone , two ribs and a totaled out machine .
The finger throttle seems to be making a come back too , might be a solution too as long as you have bark busters .
Saddle time will dictate the outcome