Unless you have a smaller trailer that doesn't need W/D hitch then the 5'er is easier to setup and hook-up test pull or no test pull. A 5'er is usually more stable to tow especially on windy days.
If I were soloing I'd have to really look at what I intended to do and where I intended to camp. Small trailers are great unless you have to spend a good bit of time in them and then the walls start closing in. Bigger trailer are more trouble to tow and to park, a lot of parks just aren't setup for trailers over 20 feet in length.