I've never seen a difference that big, but a while back I noticed a similar problem. I'd been having motor cogging problems when the VESC switched between sensored/sensorless during acceleration.
I played around with the sensorless ERPM value. I found that forcing the VESC to remain in sensored mode by setting the ERPM switchover point really high (higher speed than the motor would ever reach) meant I would have no cogging, but the peak power/speed of the motor was reduced. In my case it was not a huge difference, maybe 10-20%.
This problem happened back when VESC firmware was around version 2. I no longer have that same setup, but that motor is on a different bike with another VESC running newer firmware. It no longer has cogging problems, maybe the hall sensor tracking got improved at some point.