Well, I don't have any experience with long fifth wheel trailers.
However, I am now a huge fan of the form/size of hybrid campers. I have a Rockwood Roo 233S and love the versatility of the space of this trailer. There are 3 queen beds, a spacious living area with slide out U-dinnette, and a pretty decent bathroom/glass shower. In total you can sleep 8-9. It does this in a 25 ft trailer. There are certainly compromises here, but it works great for us.
We just completed a 5,300 mile road trip and I can tell you I would not want to do that with a 39 foot trailer. Navigating is the issue - getting in and out tight areas will definitely raise your heart rate. This includes getting in and out of campgrounds (many are exceptionally tight), gas stations, parking lots, etc. etc. I had many stressful moments in my 25 foot trailer on my trip and could not imagine the possibilities with a significantly larger trailer.
I suppose it boils down to experience and comfort with larger trailers. Less trailer in undoubtedly easier when it comes down to navigation and maneuvering.
For us, we are definitely in the less is more category.
2016 Rockwood Roo 233S
2013 Ford F150 SuperCrew 3.5 EcoBoost