I have one of the square Grace hoops on a stand. I found that the square hoop did not hold the sandwich as securely as a round hoop. There are many quilters who really like them, it's just that I'm not one of them.
That said, I do like having a hoop on a stand. It's a lot sturdier than balancing the hoop on my lap, but I am used to quilting on a full size floor frame. I recently bought a Jasmine Heirloom hoop on eBay. It was expensive, but so far I love quilting on it so it's worth it to me.
Good luck with your search.
Janet