Well, here in Switzerland both cars are 50/50 as rarity.. I only drove the S16, never a VTS...
I know the cars are similar in every aspect, but as far as I know, the S16 always got better reviews.. basically because the 106 is more driver friendly, while the Citroen needs more concentration to stay on the road..
But as you said, they're twin, so no big deal...
As for the look, with the latest face lift for the Saxo, the 106 is my fav, but very close battle..
Basically, when I bought my 106 (1.4), I was battled between it and the Saxo 1.4, then choose the 106 because the position of the license place (back) was not in the hatch, but in the bumper
