From Team 449 Wiki
The 775pro is the most powerful motor allowed on a robot. It is slightly more powerful than the CIM, but weighs half as much and takes up a third as much space. However, this comes at a cost: They are air-cooled, with a fan attached to the motor shaft inside the housing. If they are stalled, or come close to stalling, they will overheat and become unusable within 2-3 seconds.
775pros can (and often should) be used in any application that requires more power than a BAG motor, as long as the load is not close to its stall torque. A good benchmark for this is 50% of stall torque. If the load will be going over this for more than a fraction of a second, a non-air-cooled motor should be used. But if this is the case, you probably did not have a large enough safety factor in your gear ratio calculations.
Comparison to CIMs
The 775pro is smaller and lighter than the CIM, and there has not been a limit on the number allowed in any FRC game to date. The main reasons to use a CIM over a 775pro are that CIMs are much more tolerant of stalling, and have 3x greater stall torque. As for the first reason, whenever possible you should choose a gear ratio and number of motors such that normal operating conditions are below 50% of stall torque - if this is not possible, a CIM will tolerate a stall much more robustly than a 775pro. As for the second, the stall torque of a CIM is 2.41 N m, vs. 0.7 N m for a 775pro. However, you can often just scale up the gear ratio to compensate - if this is not possible, a CIM is a better choice.
Comparison to Mini CIMs
The same as for CIMs, with the added fact that 775pros are 50% more powerful, although they still have half the stall torque of a Mini CIM. They should generally only be used when it is not possible to gear a 775pro to the desired speed or torque.
Comparison to BAG motors
Larger and heavier, but have higher stall torque and free speed. Use 775pros unless space or stalling are concerns.
Free speed: 18,730 rpm
Free current: 0.7 A
Maximum power: 347 W
Stall torque: 0.7 N·m
Stall current: 134 W