@ghost
My suggestion would be to buy the longest one you think you'd ever need. Also, get the most heavy duty one you can find. Especially when it comes to hauling equipment like an excavator. It's nice to have the room to figure out the best weight distribution so it pulls more comfortably and as safely as possible. The heavier tires always give me a little extra piece of mind and you can run the cheap, foreign ones. Just plan on replacing them every 6 or 7 years anyway, regardless of who makes them.
Tilt trailers are pretty sweet, I won't lie. I know a few guys on here love theirs. I opted for ramps. It at least gives me something that I can see when backing and I use my trailer for a little bit of everything and it helps with that too. I'm sure it adds some to the price though. You could probably get a few feet more length for the same price, maybe less. Not sure.
Also, FWIW, you can get a 22' tilt on 17.5s, direct from Kaufman, for 8190. They have a nice website that lays out all the specs, options, and prices. If nothing else, it's a good way to figure out what you want and what comes on them.
Shop the 17,000 GVWR deluxe wood floor tilt equipment trailer at 22 ft. Full hydraulic tilt for loading heavy equipment without ramps. Factory-direct pricing.
www.kaufmantrailers.com
That being said, I had an older Down2Earth equipment trailer and it never did me wrong.
@justjeepin86 bought it from me and had it for a while, I think. They're solid trailers. You'll find that most brand are built about the same anyway, so if you find something from a certain manufacturer that you really like, I'd go for it.
Hopefully that was somewhat helpful!