I use the tormek t-7 as well. It’s pretty old now but still works great. That said, I purchased the 4000 grit Japanese stone for it. I think that was a pretty expensive addition. I prefer to sharpen on it vs belts. As was stated already, makes it easy to get a consistent angle and don’t have to worry about overheating the edge. I do the initial edge with the coarse stone, dress it smooth and clean up, the swap to the 4000 grit stone for the final polish.
I’ve not looked at the t-8. I really like these machines but I’m not sure it’s worth the high price. I took one over from my grandfather who used it to sharpen wood turning tools. His health has kept him from doing much for a while.