Just purchased a fifty year old house with original windows (metal frames). Recently had a salesman in trying to sell fiberglass windows. The price was definitely more than what was expected. He bashed vinyl windows at every opportunity. My husband very trusting and takes everyone for their word. Which is really better (in your experience) vinyl or fiberglass, and/or is fiberglass really worth the premium?
I have a 30 old house that I replaced the LR & Kitchen windows years ago and spent a small fortune on aluminum. When I decided to replace the rest of the windows, I just went to Lowe's and had it done for a fraction of the cost w/ vinyl. I can't really tell any difference. I mean the expensive windows look little nicer, but as far as performance and insulation, there is no difference. As far as fiberglass, I have a feeling the only real difference is his commission.
The main thing of course is to go w/ double pane, and if you want double hung. It really depends on what your intentions are w/ the house. If you are looking to impress everyone, you might go w/ the higer end windows. If you are just looking for better insulation and function, save your money. They all work essentially the same.
One other thing, If you have brick, I had guys try to talk me in to spending a lot of money on installation because they tried to convince me that when replacing windows I should have them remove and replace the brick because if someone wanted to break in to my house, they could just remove the screws from the other type of installation (bracket and screws) and remove the window to gain entry. But after thinking about it I realized - the window is glass, all they would need to do is break the glass, so all their expensive installation was for naught.
A number of options are available, Argon filled, Lo E, tempered, etc. Some of these options have to do with insulation factors and others like Lo E prevent the suns rays from changing fabric and carpet colors. Vinyl windows are the standard for new home construction. The extra cost of fiberglass is not warranted.
You can get complete information at Lowes, Home Depot. They also sell and install windows.