It seems that the determining factor is whether you already have a bike rack. I looked at the Smart rack, and I liked it better than anything else out there (I discounted roof racks, as every time I've tried to use one I've scratched the car's roof, and I have a cabriolet, so I had visions of puncturing the canvas top).
I like the idea of a rail that the bike's wheels sit in (on the Smart OEM rack). I wasn't thrilled with the upright that blocked the hatch, or the price.
Since I already had a rack that goes in a standard hitch receiver, and that rack is hinged and can be lowered to open the rear hatch, I decided to go with a hitch that was installed at my local Rack N' Road for about $300 ($175 for the parts, the rest for install).
I've been using the rack for about a week, and it works well.
Ron