Advantages;
No set up or take down is obvious.
A pantry for food stuff. They stay stocked all season.
Closets and drawers for clothes and dishes.
Stove, oven and sinks.
Bathroom and mirror with running water.
A master bed you can exit without crawling over your spouse.
Bunk beds.
Disadvantages;
To match the size of an extended large PUP you will probably need a TT 22 ft or so.
You will get 10 mpg or less.
You will need AC on hot days.
There is more maintenance.
You can not go through a fast food drive through and other handy places.
There is a certain loss of "camping" feel.
You will typically drive 250 to 300 miles a day.
All of the above is why I bought my TT but kept my PUP.