Impact and Capability of Motor Brakes?

[Argon27]

Greetings!
We have been to two regionals and have seen several teams using brakes for balancing on the bridge. Most we've seen are done at a transmission level or use pneumatic cylinders to physically "poke" the wheels.

We have decided that we want to implement brakes on our robot for balancing purposes only.

We are weighing two options:

1. Pneumatic Brakes- A cylinder that mechanically stops the wheel (Still in R&D. Not my sub-team ).
2. Electrical Motor Brakes- Basically, we want to switch the polarity of the motor at a very low power up to x times per second to keep the wheels stationary.

We've considered the potential heat, power draws, and strain on the motors. We also know about coast/brake mode on the Jaguars. What we want to know is how many times per second the output of a Jag is capable of switching safely.

Does anybody have experience with this?

Thanks!