I have not owned a Jayco, but my impression is that the two would be fairly equivalent in quality and workmanship (i.e., nothing exceptional, but decent enough).
As for FG gelcoat siding, I'm liking it even more since my TT's recent scuffle with a pickup truck on the expressway. I had to dodge an idiot who pulled in front of me as he (she?) entered from a ramp. The pickup to my left was pretty well dented, my guess would be $3000 of damage. My KZ Spree Escape sustained a cracked plastic fridge vent, a missing side marker light, a sheared off water fill connection, and black scuff marks.... $150 should fix up all but the scuffs. An aluminum sided TT would probably have sustained major denting.