It depends on your usage .
If you plan to go on a trip that requires long distances some days you should consider the minimum length you can get by with .
On a long drive day if you have too much truck and less trailer your wife can spell you for a one hour nap each day .
Gals are not as comfortable with a long trailer .
My friend's wife wrecked their relatively new trailer because they bought longer and stayed with an F 150 .
If you have discovered that the best camping is boondock dry camping just like we have a shorter trailer is an advantage fording a little gully to park your trailer right next to the stream in a brochure ready picture spot .
We do both of these and moved way down in length and that has proven to be correct for us .
For Us the Perfect Answer : diesel / allison gmc towing a 21T Komfort that we have kept twice as long as any other .