Downside is its made by Power fist LOL
This is true, however mines been going for a few years with a fair amount of use. It is also much quicker if your doing any volume of work since you don't have to wait for the compressor to catch up every 30 secs. It is also alot quieter.
If your going with an air grinder and are planning on doing any grinding other then the occasional now and then make sure you get a compressor that can handle a 9-10CFM draw or you'll spend more time waiting then grinding.