On a steel car, it's better if you can get steel fenders - or fix the ones you have. However, there's absolutely nothing wrong with good glass . . . emphasis on "good." You may need to get two front fenders, though. I'm pretty sure I wouldn't want one glass and one steel.

In your shoes, my priorities (in order) would be:

1 - try to fix the steel fender.
2 - find another steel fender.
3. get two glass fenders.

This car has a steel body, running boards, aprons and four glass fenders.