Designing Kitchens and Bathrooms - New Bath Tub - Cast Metal vs. Molded plastic

So I am getting ready to remove my old one piece fiber glass tub with walls unit and replace it with a tub and then tile the walls. I have looked at the Big Box stores and found that I have a choice between a molded "plastic" tub and a enameled cast iron tub. The Big Box fellow said that the plastic tubs are easier to install and actually more durable than the cast iron. Does any one have an opinion or a preference or a reason for one over the other. I do not generally trust the "expertise" at the Big Boxes, but the plastic tub was slightly cheaper than the cast iron tub.... I am at a loss as to which one to go with.

Thanks

upon further searching I found the following (for those interested):

http://forum.doityourself.com/archive/index.php/t-43831.html

http://www.terrylove.com/forums/showthread.php?t=339

http://ths.gardenweb.com/forums/load/plumbing/msg052339514791.html

seems like cast iron is the way to go....

As usual, I disagree with you big box salesperson. Cast iron is quieter, needs no additional support, will outlast you with proper care. They are HEAVY!!!! and more difficult to install, because they are HEAVY. Fiberglass/plastic can crack if not properly supported underneath, MUST be cleaned carefully to avoid damage to the gel coat. But are easier to install. Fiberglass units can come as complete units including surrounds, cast iron does not.