A5 2.0 TDI or A6 2.0 TDI ?

Hello guys, I wanted to ask you what would be the smarter alternative from your point of view, namely the A5 Sportback or the A6 as a limo? Should not be much different in maintenance. In terms of equipment I insist on Xenon,Leather,MMI+ and manual transmissions. My driving profile consists of 2200km drive to work (50%Overland/50% highway) and about 1300KM private rides (50%City / 50%Overland) all month of course. So we come to about 3500KM a month, these I currently spin in a small n Seat Ibiza down and get tired of it, especially since it is a gasoline engine and swallows far too much for a 1.4, about 7.5 liters the little one needs. I decided for a 2.0 TDI engine because I want to keep the maintenance costs as low as possible. My budget is about 20,000€ ! I thank you in advance for your answers! Lg Thomas