bob - pulled one around oz and nz, and across the us. i likes it. trailer wheel tracks
along with the bike, kinda nice when you have to avoid obstacles, or need to be
close to the edge of the pavement. drawback is flying - you need a separate box
(and more weight). sometimes tough to get into small taxis or 3-wheel motos.
other drawback for some is stability - they seem to have trouble parking a single
wheel trailer. smaller wheel is no big deal, just zip-tie a spare tire underneath
the trailer.
i wouldn't use a two-wheel trailer due to the tracking issue.
an extrawheel might be the way to go if you don't have gobs of bulky stuff. (3-man tent,
heavy-duty hiking boots, 4-5 gallons of water) i assume it's lighter than the bob,
and just might fit inside your bicycle box.