The main reason why I do like the reflex clamps is that with a weight I do find that with some records I can see that the edges are not in good physical contact with the platter, and just judging from what I have seen with my eyes, it seems that sometimes a weight alone can even make this worse. Of course it may not matter with most LP's, but it does seem to matter with some. Re weights, I was honestly just playing around; the AT618 is a good bit heavier and wider than the supplied weight, and also nicely rubberized, which may or may not help to damp resonances. I have not had time to really compare them sonically; honestly I just surreptitiously added the AT to one of my Amazon orders b/c I figured the Finance Dept. would let it slide and I could always return it or give it to a friend. But I will get to it this week. I don't really obsess about this kind of thing sonically; it's just a cheap tweak, and no audiophile can resist a cheap tweak.
EDIT: If people want to try different clamps/weights, be aware of the height. The supplied weight is 30mm high; I wouldn't go much higher than that, but that leaves plenty of choices if you want to play.