Nylon or Steel Rollers

I will be purchasing the 81-057 replacement wheel, an exact fit. My only question is which version should I get, the Nylon or the Steel Wheels.

A couple questions:
1) Which last longer,
2) Which will make the door roll easier and
3) Which one will be quieter if they are on a new track.

All my doors are under cover and are not exposed to rain. My only concern is that I live on a canal which has brackish water so there is a salt in the air. Also it is Southwest Florida so there is a lot of humidity. So, Nylon or Steel?

One more item to consider is I will be purchasing the 80-102 Track cover. My track is 3/8" high and looks to be 1/8" wide. Is this the right track to use, it does have a mushroom shape but others seem to have a ¼" wide track. Are they held in with pressure or do I need to add a glue or something. Also, and the big question is: After they are installed will these wheels fit on them.

Thank you