How many miles a year will you be towing?
If you are going to be traveling a lot with the trailer, than a three axle and 32' may be a good choice because of the extra space and spreading the load on six tires vs. four, but If you only drive a thousand miles or so per year, the tire may dry rot before the thread is warn down.

I have a 28' two axle that works good for me. When I originally bought it, it had the six lug 15" rims, and when packed with a #4,200 pound car, and tool chest, and extra junk, the "D" load rated tires were taking a beating. Last rear I replaced the rims/tires with 16" rims and "E" load rated tires. Anyhow, if you find a deal on a trailer and it has 15" rims, it is not that difficult to replace them with 16" rims and tires.

I looked for quite awhile before buying my trailer, and found a good deal where the guy was upgrading to a 40' trailer.

Using a 1-ton 2005 Ram Diesel to tow it with.