Car appreciation... the aesthetics, the engineering, etc

ULEZ compliance maybe?

Pretty sure both will comply, but iirc there are EURO-6 engines available in the Mk6.

But basically it's the standard reasons you'd expect for buying a new model with few changes.

@Dammit - if what you're asking is whether the Mk6 was a big leap forward, my understanding is no. It's a light refresh.