I fished fiberglass in the 70's and then 15 years ago I earned an Orvis 5wt SF rod with spin reel & fly reel. Thought it was the greatest until 2 yeas ago I compared them; no comparison for me (IMHO).
The Glass was/is superior. I will tell you this; if you are cast hard with glass you are over casting. MOST glass is slow so you get that wonderful rhythmic feel like watching fly casting in slow motion.
Don't try to cast it like graphite; it's different. Slow down a lawn cast first and feel it; great for reach casting to DROP a fly like a parachutist coming in for a landing.
I now have 5 glass rods and 5 graphite's are for sale.