Wot ru talking about?
Point 1> You get a better warrenty? How? You get exactley the same warrenty with both cars, 3 years, both covering the same things.
Point 2> Arosa a better car? U state in ur second para that VW quality is something to be praised. Why not buy the real thing if u want the quality, thats where the extra £1500 comes in.
I can see the point ur trying to make but the simple fact is that whilst the two cars are very similar there are striking differences. VW offers a much wider range of engines (arosa offers 3, vw offers 5 (admitally not seats fault)) and not only is the interior of the lupo a much better quality but it is in my opinion a much nicer place to be. Yeh the arosa is a much better budget buy, but it is noway the better car to buy.
P.S and as for showing a range topping arosa and a bottom range lupo, take a look at the lupo gti against any arosa.