My feeling is a little more trailer is a lot better than just enough trailer. I would go 18' and 5000lb axels. You'll never complain about having too much room on the trailer. Plus, the cost and weight difference isn't even that much, I think you'll be happier in the end....
Is it a tilt trailer?
I'm happy with my 22' deckover power tilt Diamond C. I upgraded from a 16' gravity tilt. Steel deck & 7k axles. Got it used at an auction, small local OEM. I assumed I was upgrading to another longer & nicer gravity tilt, but went another way. A gravity tilt loads a vehicle much nicer. No ramps, low angles, nice. But if you have any impliments (or machines) over 81-83", you have fender clearance issues. The back 10-20% of the deck isnt usable due to balance issues (deck needs to pivot dead center & that has to be between the axles). Can be resolved a bit with a small fixed deck up front. But the killer for me was loading other stuff. Fenders just got in the way. So I ended up with the deckover power tilt.Is it a tilt trailer?