I have a KZ Durango Gold that's 6 years old bought new, I have had zero issues with it. Most RV's are built in Elkhart or Shipshewana IN. All three your looking at are subsidiaries of the Thor corp. KZ did authorize mobile repairs on the Golds as they were built for full time living, you may want to see if the still do.
Now lets talk warranty, it is not like autos & truck you take it to the Ford dealer. RV warranty will be take it to your selling dealer where it will be weeks to months getting fixed. You want to learn how to fix the minor issues yourself, you will have 120V, 12V, water, holding tanks and possibly hydraulics. Learn the systems, how they work and carry some basic tools. The appliances inside will be from a few different manufactures, Coleman, Suburban, etc just installed by the RV manufacture. During the first year a call to the appliance manufacture will likely get you fixed faster.
Look for a pre delivery check list, several on line, get one that's extensive. When you pickup your new RV have them show you have every system works, video it for future reference, do not let them rush you. Have them power it up and get connected to water. Have them fix anything you find BEFORE you take possession. Then plan to camp a night or two at the dealer or an RV park close by so you can bring it back fr anything you find. Open every cabinet, drawer, door, slide etc you will only get the one chance to get it fixed before you take it. I have owned both Jayco & my current KZ all three you have picked are good quality not what I would consider entry level. Good luck & happy camping.