1. metal rack with sleeves:
Classic - noisy, galvanized (where the galvanization wipes off - it will start to rust). And maybe more wear than plastic (but let those who assembled them say - I had few plastic ones) but certainly more resistant to impacts and strong pressure than plastic - for gates say from 200 kg up. In industrial applications and harsh conditions, only metal ones are used, and for large gates, additionally thickened.
2. teflon toothed rack with screws:
It's not made of teflon, but reinforced polyamide or nylon and has a metal insert, besides there are two types - "slimmed" and full thickness - if it comes in - I would take the thicker one
It is much quieter than metal, of course it does not rust and is more resistant to abrasion than "lubrication" with sand, but it is a material which (despite the thin metal core) has lower shear strength than steel.
I would use in home gates, exposed to water splashes, but lighter ones - up to 200 kg.
There is the issue of fasteners: - the steel one is mounted to the bushes, which in the simplest (but the strongest) version are simply welded to the gate's guide profile - to the detriment of the gate's anti-corrosive coating - if it is ordinary painted - nothing happens - welds are protected with liquid zinc, undercoat, paints and that's it. If the gate is galvanized or / and powder painted - the stairs begin. For such cases, here on the forum were descriptions of the use of various patents of the rivet nut or even threading holes in the profile wall and screwing through the bushes and the profile wall of closely matching pins - and both are not sure. And another difficulty - these patents can not interfere inside the profile with the horizontal roller of the guide carriage.
Fixing plastic strips is (in theory) simpler - it is simply screwed to the profile with self-drilling screws (and this fact limits the use of such strips for light gates - and to the statement found in the descriptions: "up to 600 kg" I would approach carefully) and here the advantage: clean assembly without welding, the disadvantage - the same as described above - must be assembled so that the screwed part of the screw does not interfere inside the profile with the guide roller (of course, you can mount it like steel, ignoring the factory fastenings - through the bushes - only carefully with welding nearby - after all it's plastic ...).
So if you have a light gate - try plastic (considering the pros and cons of mounting methods). You can always (if it does not work) mount metal.
