I've wrestled with the fiberglass vs vinyl question myself more times than I'd like to admit. Honestly, fiberglass does handle temperature swings better—less expansion and contraction means fewer gaps over time. But in a moderate climate, the difference might not be as noticeable as manufacturers want you to believe. I've seen vinyl windows perform just fine for years without issues, provided they're installed correctly (like you mentioned).
That said, fiberglass does have some advantages beyond just temperature handling. It's generally stronger and can support larger panes of glass without sagging or warping. If you're going for bigger windows or want something that'll hold up longer structurally, fiberglass could be worth the extra cash.
But if your main concern is insulation and you're not dealing with extreme weather swings, vinyl might be perfectly adequate. I wouldn't call it marketing hype exactly... but manufacturers definitely push the premium stuff harder than necessary sometimes. Trust your gut—you're not crazy for obsessing over this stuff; windows are a big investment and worth getting right.
Totally agree—vinyl gets a bad rap sometimes, but it's honestly solid if installed right. My cousin put vinyl windows in about 8 years ago, moderate climate, zero issues. Fiberglass is nice, sure...but sometimes the extra cost just isn't justified.
Vinyl can definitely be fine, but I wouldn't dismiss fiberglass so quickly. Had vinyl windows put in about 12 years ago, and while they've held up mostly okay, a couple started warping slightly after some intense summers. My neighbor went with fiberglass around the same time—no issues at all. Sure, the upfront cost stung a bit, but now I'm thinking maybe he made the smarter long-term move...
I hear you on the fiberglass vs vinyl debate. When we built our place, we went fiberglass after seeing similar warping issues at my parents' house. The upfront cost definitely hurt, but zero regrets so far—especially after last summer's heat wave. Hang in there, window shopping is no joke...
Fiberglass definitely has its merits, especially in extreme climates. I've seen vinyl hold up decently in moderate conditions, but once you factor in intense heat or cold, fiberglass usually comes out ahead in durability. Still, insulation ratings can be tricky—have you looked into how different glazing options (double vs triple pane, gas fills, coatings) might impact performance? Sometimes those details make a bigger difference than frame material alone...
