1 get the ureathane , fiberglass is rigid by nature and can never be more impact resistant than plastic.
2 Make sure you get it painted by a good body shop ,otherwise it WILL chip right off on the front end looking like you traveled 3 000 000 miles behind a transport truck. It needs good primer and almost no matter who you get a kit form they all need a slight bit off finishing ,usually just to flatten out a few spots from a mould by using a sanding plane to level the finish perfectly.
After that ,the higher you pay the better and easier it is to install.
So if you get a $700 kit expect to spend 800 to paint and 500 to finish and fit it
or buy a $2000 kit and spend 500 to paint and install it