This is only my opinion, but I would tend to think that you would want a more dense felt, which typically translates into a harder felt. The reason being is that a more dense felt is, the less likely it is to collect any small metal chips and retain them. The felt wipers should help spread way oil, but should also do a good job of sweeping chips off of the ways without retaining them.
I made some rubber wipers for my Logan lathe, using the rubber strip from an old window squeegee. The felt wipers are still used and retained by the sheet metal cover, but the hard rubber wiper is mounted on the outside of the sheet metal cover, using a longer screw and a washer. I have no clinical proof that the new setup works any better than the original design, but I tend to think that it should.
I have not made any rubber 'pre-wipers' for my Clausing 8520 just yet. I have considered it, but I am leaning in the direction of making some sort of way covers instead. I tend to think that keeping the chips off of the ways to begin with would be better than trying to wipe them off once they have landed there.