there is a slight downside as you will use a bit more power because of the torque increase. Digi's just add to the power usage even more.

I have a GP Super Stearman using 8 5645's (way overkill) and a 2400Mah 6 volt systrem and get about 4 flights before it's to the point I want to charge. I could probably get 5 flights but why risk it.

The 5645's are the same as the standard 645's but are digital