As others have said, you need both. I've had bench grinders many, many years. My current one looks like
this one except I have a 6" model instead of 8". If you use an angle grinder, whether electric or air, you need a good vise to hold the item you're working on. I use a 4" vise myself. Down in the country, I had a
Craftsman 4.5" electric, but now all I have is a pneumatic
angle die grinder which is great for putting a really fine edge on tools.