By all means buy a Grripper. I have a pair of them and I use them all the time on both router table and table saw. They simply work better and give me more confidence than anything I've ever tried. However, I think they'd make a poor substitute for a vertical coping sled.
“We should be careful to get out of an experience only the wisdom that is in it and stop there lest we be like the cat that sits down on a hot stove lid. She will never sit down on a hot stove lid again and that is well but also she will never sit down on a cold one anymore.” - Mark Twain