If you already have a good truck or other towing vehicle, then the cost of a trailer is far less than the cost of an RV.
On the other hand, having an RV may mean you need to tow an additional vehicle (toad) for sight-seeing, grocery runs, etc. If you already have a towable vehicle, the the RV could be the better way to go.
For us, we wanted an RV to avoid hotels/motels and the ability to stop almost anywhere. It ended up that we almost always stay at an RV park with full hookups. Also I got a great deal on a towable vehicle.