I like the one that attaches to the trailer. I had an RVQ on my Starcraft Hybrid and really did like it. I used the propane from the trailer and it stored in a bag which kept things clean.
That said, I am a believer (in most cases) in you get what you pay for. I have purchased many portable BBQs, most of them the cheap variety over the years. I did not want to pay the extra for a "fancy" one. These BBQs worked well but they did not last. Grates would warp and burners would, well, burn out. If you can get one for half the price but it only lasts a third, or less, of the time you are not saving anything.
I purchased a Webber Q200 which was the larger of the two offered at the time. It is a bit of a beast but with two son in laws and families we needed the extra grill space. This thing continues to work very well and performs like new. It isn't all that hard to clean either.
What are you looking for? One that attaches to the side of the trailer has its advantages. If you want a good table top BBQ, take a look at the Webber.