The problem I have always found with slugs is that they are never long enough to slide properly so they bind in the slot. And if they were long enough, then the sail would stack too high. The manufactures of the masts SHOULD provide a good slide system to start with, rather then leaving it to the aftermarket people.
But this is why I went with the Tides sysytem. At a boat show
I tried my best to get it to bind without success, SOLD! Where as, the bearing types, if I twist them or kink them just right they would bind or at least was hard to move.
And the Tides had a shorter stack height. The install was so EZ vs the tracks for the bearing types. I didn't even have to leave the deck
. I did have to pull the mount for the gooseneck, but no big deal.
Another positive but unlikely to happen, if you were to hit the Tides track with something it would bounce off. But the solid tracks of the bearing type would get damaged and the car may not like that much.
Another thought would be a broken mast
at sea, which would you want.