It's a pity they didn't fit PT6s to the Rockwell instead of the Garretts.
Garrets are in most ways better than PT6's:
They're more fuel efficient.
They're quicker to respond.
They have higher TBO.
They're easier to find replacements for.
They're cheaper to run.
Drawbacks are that they require more power to start up and are harder on the batteries. They're also noisier.