I have used a trailer for 10 years and 4-down for 3 years. If you plan ahead you will rarely need to disconnect the trailer. In those 10 years of travel I encountered one RV park that made me disconnect the trailer, not because there wasn't room for it, just because they didn't "allow" trailers, but they didn't tell me that when I called.
It's all about advanced planning by calling the RV parks and specifying the site length you want.
Now that I have done both I can say that I rather use the trailer because I like the ability to back up and the fact that there is no wear on the toad. In my situation, it is my opinion that the trailer is less drag than the flat towing.