The two biggest factors for me in picking out our trailer were the aluminum panel siding and the 5/8" tongue and groove floor. Jayco's vacuum bonded fiberglass does seem to be better than most based on my experience with our 2006 Jay Feather and I did like how easy it was to clean and keep looking nice. I wanted stick and tin this time because I know I can tear into the trailer with my skills and fix some rot or other internal problem if needed. If a fiberglass side needs to be re-laminated, I'd be up you know what creek and be paying someone else big bucks for this. Plus you see some pretty old stick and tin trailers in pretty nice shape if they were somewhat taken care of.
Both styles have their ups and downs, but that was my reasoning.
I wasn't wild about the sandwich floor construction in my Jay Feather either - the plywood in my Jay Flight is much more sturdy.
Also, if one of the Jay Flight line trailers isn't "big enough" for you you must have some pretty extreme trailer needs! I have noticed that there are few if any aluminum sided 5th wheels being built now though.
2012 Jay Flight 29QBH
2003 Dodge Ram 2500 Cummins H.O. 48RE
Equalizer 4-pt sway control hitch
Prodigy P2 brake controller
2006 Jayfeather 29Y (past Jayco :))