There are some great trailers out there. BRP makes a very good trailer. The Bushtec is also a very nice unit. Small tire trailers are OK on smooth pavement. But they spin much faster (watch the wheel bearings). Rough roads and potholes can really give them fits.

I think the BRP trailer is the best looking, and maybe the largest storage area, of the choices. However, when it comes to function, it's hard to beat the Bushtec. Not as stylish as the BRP (IMO). But those large diameter, small width tires make them very easy to pull. They track straight and ride smooth even in difficult road surface situations. I've seen them hit some big potholes at highway speeds and not bother the trailer or the tow vehicle much at all. Not as critical on a Spyder as it would be on 2 wheels. But still a factor to be considered.

Have not ridden with an N-Line trailer. But other than the added length created by the design. I think it would be extremely smooth, stable and easy to pull unit.

Good luck with your search! A lot of worthy choices is a good thing.