Trailer is much more adaptable and can carry more, but a lot more expensive including towbar. At least with a towbar you can fit a decent bike rack too.
I used a small trailer for camping, fitted roof bars and 4 bike fittings on top too (more aerodynamic than roof top), drove to the alps at 80mph all the way no problem.
And you can still hire/borrow a bigger trailer if you need to shift large stuff occasionally.
Both need storage space though – a roof box fills a lot of shed/garage, trailer can be locked in garden.
Trailer is much quicker on/off too.
Trailer it is then!