Pros/cons?

Sure thing, Ross. Right off the bat, steel wheels are stronger and hold up much longer than nylon. The disadvantages however are that they aren't as quiet and are susceptible to corrosion. If you live in a salt air environment, then that's definitely going to be a concern.

All that aside, in terms of smoothness and ease of use, they're basically the same. The biggest determining factor in my experience is whether you live in an area where rust is a concern. If you do, then you want nylon. If not, then the sheer durability and longevity of the steel wheel outweigh whatever minor benefits the nylon may offer.