The amazon page gives a bit of a rundown on the difference. A clamp “clamps on to your spindle securing the record tightly to platter. A weight does essentially the same thing by obviously adding extra weight. The reason I went with a clamp is because I didn’t want to add stress to my direct drive motor and I do find it effective. Though, aesthetically I think a heavy puckish weight looks cooler.
Another thing, with that 120 make sure you’re running a decent mat (even just cork is fine) because that hollow metal platter can get a little ringy if it’s too hard or too thin. Buuuut rubber or thick foam can get muddy. You might need to experiment.