Panniers are fine, but I now prefer a trailer.
Main reason is that my bike still rides like an unladen bike, panniers make my bike feel like its changed from a sports car to an RV.
Trailer seems less affected by cross winds.
Trailer is easy to detach at campground, overnight stops.
Cars seem to give me more room on roads than panniers, maybe they think I'm pulling a kid?
Trailer seems easier to pack/unpack.