508's engine noise is fairly better insulated than K5.

225/45/R18 is definitely going to make your feel hard bumps on the road, compare to 508's 235/45.

One pays less road tax than the other. One has better torque than the other. One pays less 20k than the other.
Both will share the same servicing pain...ahhaaha..

All depends on how buyer sees it.

I'm curious as why some of the people does not know about the DSG gearbox issues on some of the VW models here... and laud about it's greatness...