My cat is medium-haired and he drops a lot of undercoat. I looked at the Zoom Groom but it doesn't seem to me like it would do anything on a medium- or long-haired cat... it looks like it would be better for a short-haired cat.
I got the Furminator and it works very well. You do have to be more careful with it, but it doesn't take long to get the hang of it and the cat seems to like it (he sometimes lets me use it on areas where he usually objects to grooming with other tools). I don't use it every day... I alternate days with one of those loop-shaped grooming rakes; the Furminator seems to get off slightly more hair. I think it would get off even more if my cat weren't tricky about grooming and would let me do more.
Since you haven't gotten your cat yet, though, it would probably be better to wait and see what the shedding is like before you buy tools. You may not even have a shedding problem with the cat, and find that a regular brush is all you need.