Steel skis were solid, but dragged a little in the snow. Polaris put the skins on them in an attempt to reduce some drag, but that came at the expense of cornering. Plastics will be a nice upgrade as you'll get some cornering control back (that you likely didn't even know you were missing) and not have any extra drag from the steel. Also, being a little lighter, it should help with steering response too.
Any Polaris plastic would do you well. Some of the aftermarket ones are really great for certain types of riding, but I don't know anyone running anything besides the Polaris skis at this point. Also, that's all that I have had on any of my last three or four sleds.