Flip of a coin is pretty accurate since they are pushing these rigs down the assembly line and out the door as fast as humanly possible. Both Jayco and Grand Design have good customer service as most have reported, purchasing from a dealer with an above average service record will aid in getting warranty issues dealt with correctly and (hopefully) in a timely manner.
It pays dividends to be handy with tools before and after the warranty expires, instead of hauling our TT into the dealer and letting our rig sit for some unknown time, they ordered the warrantied parts and I installed them myself. Too many reports of RVs just sitting for weeks, many incidents of batteries being totally dead upon pickup, truly degrading lifespan of battery.