You have 5 0r more pieces to deal with off the bike, with panniers.
with all your stuff in a trailer, there is just one piece,
and it has it's own wheels.

if you want to go on a back county hike in the middle of your trip
then you can put your backpack and boots in a trailer.

there was a Swedish guy, rode his bike to Nepal, climbed Everest,
then rode home.