i use the autolock 2000, when i got mine it was the best in the test ( 2 yrs ago) but Disklok has redesigned theirs since then.
I can only speak for the autolock - the lock mechanism is sometimes fiddly to use and to be honest it is a major pain in the arse, the locking mechanism looks a bit cheap but seems to work ok. my friend has the disklok, the advantage of that is it covers the whole steering wheel and rotates around it, and the bar folds inside the cover, and i believe the disk also folds inside itself to make it a more smaller when not in use.
another option is a device called " bullock" it clamps around the clutch and brake pedals, i have used this many times in S.Africa, where it is very popular. http://www.bullock.it/inglese/tipe.html
robbie.