I've been using folding trailers for the last 7 years behind my Jetta. A 4X8 fold-up fits up nicely in the garage wall and can carry a Sled, ATV or 2 bikes easily. Plus can be used for landscaping (with sides) or tarp.
My old one lasted 6 years before I got rid of it (sold for $100 Can) - and just assembled another HF for $259 (they go on sale regularly) US plus taxes and decking. Just make sure you get one with 12" wheels!
http://www.harborfreight.com/1195-lb-capacity-48-inch-x-96-inch-heavy-duty-foldable-utility-trailer-with-12-inch-wheels-90154.html
Metal - A 2" ball can be switched to a 1 7/8" ball in a minute (unless you have some wired permanent mounted hitch with integrated ball)? On my 04 Jetta TDI I have a Draw Tite hitch and works great.
The Red trailers are a little to pricy for me (they are better than the HF ones - but how much better?) -and the trailer in a bag aren't cheap also (unless you can pick up a used one?).
Best of luck.