Trailers are usually more expensive... donno where he got the idea being cheaper.
Racks are nice, give you a bit of extra storage. The only issue I would have with one, is if you over load it, you have a lot of extra weight up top making a roll-over more possible. But if anything, a rack that can be removed for top(soft or hard) would be best. I think most racks I have seen bolt to the tub, which is good.