"James Nipper" wrote in message
news



I see they commonly have 4 1/4 inch and 7 inch sizes. Is there
any
common reason why one is generally better than the other ?

4-1/2 is big enough for pretty much everyone.
Tim the Toolman Taylor may need the 7" grinder, but few people do!
The smaller grinder is much easier to handle. I would not get a larger one
unless you plan on opening a welding shop!
Greg