I do both. I think it all depends on where you are going and the time of stay. It is way easier to hookup 4 down vs trailer so if you do a lot of short stays trailer may not be worth it. Also as mentioned location can be a factor. If there are pull thru's and you plan on staying for some time trailer wins hands down. If you have a tilt trailer even better because manual ramps can be a PITA along with hooking up straps.
Someone mentioned they feel the trailer tows better due to less drag than 4 down and I feel the same way.