Careful with low-end urethane moldings. At times they aren't exaclty the same profile...pieces can be off just enough to make a difference...if that matters to you.
Also, in general, the longest they come in is 8' pieces. More butt joints, depending on the size of the room. Use the proper glue for adhering, wood glue is not the answer.
Urethane is a good choice when you're trying to install a complicated molding that would otherwise require a 4-6 piece build-up from stock wood moldings...though I don't think that's the scope of your work.