As Gary said- we use T-64's and run them of a pair of vyper esc's.

The T-74's are not as reliable. More power through the small pinion- this is the weakness on the T-64's so putting more power through it makes the issue exponentially worse.

Also the added weight hanging off the back of the back of the gearbox can cause the casting to break (i asked the same question to a few teams while at Battlebots and that was the general opinion)