I own a 20 footer that I restored and I own a 16 footer from the same custom welding shop that I ordered when I started. The right size for us would be 18ft I got a lot of space on the 20 footer I don't use. What Id like is to lazers with trac vacs on one crew they are 9 feet long with that configuration so 18 feet would fit them perfectly.
The longer your trailer the longer your rig and parking can become and issue which I know all to well. My trucks are 23 ft from the front to the ball hitch and my trailers over all length is 25 feet making me 48 feet long. My short set up again the truck is 23 feet and the trailer is 20 feet making that one 43 feet long. Depends where you work but I got neighborhoods thats no issue at all and others where you are blocking one or even 2 driveways no matter where you park it.