Hi Elaine,

I'm a little surprised you can fit the three seats into the back of all of those cars, but as you've only asked about reliability and performance, then I'll assume you've got that sorted for yourself.

Now, performance will depend massively on which engine each of the cars has. The Tucson, presumably, has the common 1.7-litre diesel and it has adequate performance. Most of the A4 Avants and Superb Combis are powered by 2.0 TDI diesel engines, and they'll feel far livelier than the Tucson. 

Nonetheless, the Hyundai fights back with a great reputation for reliability and a longer warranty from new. It would have had a five-year warranty and still have a useful portion of that valid. The other two would be similarly reliable as they share quite a few components. If it is the 2.0 TDI engine they have, then it's quite dependable, though it's likely to come with high maintenance bills if you're only using the car for short journeys, as the diesel particulate filter and other diesel components can clog up badly.

Feel free to come back with more information on each and your likely driving use if you want more help.