Velocity is OK up to your threshold limit and what you can shoot accurately. At an extreme low velocity, a sedate 950 fps with a heavy (400 grains and up) hard-cast, gas-check bullet it is possible to bring down a buffalo. It takes a buffalo some time to expire because of its great size normally.
But sending a heavy bullet over 2000 fps will increase recoil and make accurate bullet placement less likely IF the revolver makes you flinch from the concussion of force. High velocity can also reduce penetration of heavy hard cast bullets as tests have shown. So 1350 fps to 1400 fps is a good maximum to reach. 1200 fps is a good minimum for penetration reliability.
A Cutting-Edge solid bullet can also be a good penetration asset at top velocity due to ultimate bullet integrity. It exhibits this being made of only one tough metal. It will not be deformed from higher velocity as a hard cast bullet might.
But I digress. Use what you can safely shoot and hit your mark with. And use a bullet that will perform as your needs dictate. Animals deserve our best efforts to kill them quickly and humanely.
So velocity is good, but bullet integrity/performance and bullet placement is more important in making a clean kill.