If you have a large enough truck, I'd skip on a rollback truck. I used to own a box truck, and I now run truck and trailer combos. The trailers are much nicer to work with, and when the box truck broke down, it was more inconvenient than losing a truck.
I'd go with a flatbed trailer. A car dolly will only do one thing. If you want to tow a 4x4 F150, you're disconnecting driveshafts. If you ever want to move an Audi with quattro, or a Subaru, you can't. With a flatbed trailer, just use some chains and binders, and you're off.
The flatbed will also work with other things, too. A good flatbed may cost a little more, but it's well worth it in my mind.
Bookmarks