If I had a powerful mig welder I'd pick it every time over stick. But, you'll need more power than a 120 volt wire feed unit unless you are just welding thin fender material.
If you already have an AC/DC buzz box you can do whatever you need. Even just an AC only one can do it if necessary, but some overhead stuff will be a bit harder. I usually turn the trailer over and do the underside welding and I use my AC welder more than anything else. I wish I had a nice mig machine, but I've done a lot of projects and a few trailers with stick.