I have I am guessing five bench grinders of some type or the other, and hand held shop grinders, (and one buffer)
IMO if you stopping the grinder your not using the correct grinder wheel, or you are not using it correct,
I think most of mine are 1/3 hp and one is 1/2 hp,
If I have a heavy or a lot of removal I take a 4" or 7-9" hand held grinder to it,
the majority of the grinding I use the bench grinder for is to tool sharpen, and light removal or wire brushing,
If your welding I suggest a 4 or 5 inch hand held will do about 80% of your grinding needs in most welding situations, and if your in to hogging off metal then get the heavy duty 7 or 9" grinders by a name brand company,
my old grinder is a grinder that was sold by WW Granger, sold 50 years ago, and the others are imports, In my opinion there good for the money,
but when grinding let the wheel do its work, don't force it, it will most likely grind faster with lighter pressure with he proper grit wheel than forcing it and slowing down the machine,
if slowing them down then get a heaver larger grinder, ( I would guess 85%) of all 6" wheel grinders are 1/4 to 1/2 HP you most likely would have to step up to 8" wheel for more HP, the you may start to get in to 3/4 to 1 HP,
if you really want get a old head, belt driven and put any size of motor you want on it, if you a 3 hp 6" grinder then you can build one,
for 40 years I used one from a belt driven head I picked up at a junk yard, (now know as a land fill), and an old may tag washing machine motor, and the reason I am not using it any more is I need the room for some thing else and it was wall mounted, still have it just not using it, since I have 4 other bench type grinders in that shop,
No prob