Even though you will be using in fresh water, I'd go with aluminum. It will be lighter and resale will be better. Check out Nextrail, they deliver to you. I have one and am real happy with it. Just towed boat from FL to NY and it was great. Mine is dual axle (torsion, no leaf springs!) (6000lb) w/disc brakes on one axle. Give em a call.
http://www.nextrailofamerica.com/