DO NOT..repeat NOT touch either of those with a bargepole if you plan to use it anything like regularly
The type that you link to, the cheapies
that clamp around the ball, sway side to side, tilt back and forth, swivel around and are invariably spot-welded badly enough that the tension of the clamp can break the welds dumping your bikes on the outside lane of the M1
Not all are bad though, the budget ones which
clamp to a plate fastened behind the towball are fine.
http://cgi.ebay.co.u...em=260656184415
or from the same company but with free delivery (though the free delivery is on a "lowest priority" dispatch so can take up to 10 working days, the
ebay option is a fiver delivery but quicker)
http://www.discount-...Mounted_Carrier
It's only fair to disclose my interest in the listing as I manage the online sales channels for this company so by all means look around for similar. This is the rack I use and it had all the advantages of folding up compact, but clamps firmly and doesn't move. As an extra, I pass one long strap up to my tailgate, around the tailgate hinga and back down to the rack framework to give upper stability and reduce any flex on the plate (though that's probably overengineering and down to the fact that I had the original incarnation of this that wasn't reinforced on the plate, thus the plate had a tendency to bend (the plates are now reinforced and profiled to prevent bending)
These types sometimes need a spacer plate for some profiled bumpers (you can see on the mk1 Avensis pictured how close the rack sits to the top of the bumper)
I've had it some time and it's reliable and sturdy enough - mostly use it for one bike but have also carried two bikes plenty of times without issue.
If you don't have a bolt-on towball they you will need some kind of clamp-around rack...I'd recommend looking at the Thule and Pendle options if that is the case