I have a bench grinder. Ive had it for 5 years and only used it for car/truck stuff. I have an angle grinder. I ve used that the most, with both cut off wheels and with a grinding wheel, but always for house/car/welding projects, never bike stuff. I have a sawzaw too, and have used that a lot. Never for bikes.
Now, i did buy cloth wheels for the bench grinder, and the polishing stuff intending to polish bike stuff, but, it will make a huge mess doing so, and i havent gotten around to it yet.