Keep in mind, if you're going to repurpose switches, Make sure to buy a desoldering pump.
Preferably a desoldering suction gun, if you can afford it.
These switches are not meant to be resoldered, The housing where the copper is will melt slightly. The less skilled you are at -Desoldering- the longer you have to keep heating it. The longer you heat it, the more the internal mechanical alignment is affected.
This culminates in keys chattering, inconsistent key feel, etc..
The sliders make very little difference, the well worn HOUSING in vintage switches is what's responsible for the bulk of the smoothness.
THAT SAID, vintage black is still not as smooth as Cherry MX Blue. MX Blue has the smoothest travel of any switch because it has that white internal slider with huge clearances, so you perceive overall very little friction.