If you look at the expensive ones and the Chinese junk you'll see that the slide part on all of them is all but identical, that being a slide bar and a weight. Personally the one I've got was home made probably 30 years, or more, ago. It's not fancy but it has never let me down. The main thing with any slide hammer is the attachments. The way mine is made it uses a 5/8 fine thread, which is fairly standard, for the attachments to hook to it. With a standard hook up like that I can use off the shelf things like the hooks, etc which is good. Even better is the fact that when I am in the field and need something special I can simply take a 5/8 fine thread nut and use it as an attaching point for whatever I need. This works great when I need something special, like I did the other week, where I had to make one with a metric bolt long enough to get down in a hole and pull a coller out.
Like I said, the slide parts are all going to be pretty close to the same other than the slide might be a bit sloppier on the China ones, etc. Other than that just make sure that the attaching point is standard. From there you can get the name brand attachments from places like OTC, etc.