A lot depends on the condition of the blade, the number of blades and how long you leave in the tumbler.

If the blade is not that rusty and you only put in one blade and not leave it for too long, it will probably be ok, but banging and vibrating against the sides of the tumbler will round off the edges of the razor, if left for a length of time.

A razor blade, steel wool and WD40 is much quicker then, hand sanding or buffing is quicker and gives you total control over the finish, etch and the edges.

Or you toss it in and hope, there is no control over the outcome. I have done both ways… I hand sand and buff, haven’t use the tumbler for razors for years…