I had a 2014 Jetta Premium with Navigation for seven months and 22,000 miles before trading it in on a 2015 Audi Premium Plus with lots of bells and whistles three months and 15,000 miles ago, so the comparison is not exactly what you asked for but should be pretty close.
If I had to describe each car in a word, I’d say the Jetta is “nimble” while the Audi is “solid.” I really liked the Jetta and would probably still have it if the driver’s seat were more comfortable. The car was an ideal size for me, visibility all around was good and it was fun to drive. But the seat, even with the lumbar support cranked all the way up, wasn’t enough for my back. In addition, the support was too high to be effective. I solved that problem, sort of, with an old rolled up kitchen towel under my lower back (nice thing about kitchen towels is that they are infinitely adjustable and virtually free) but that still left a lack of thigh support that became achingly apparent on long drives. Since long drives are the name of the game for me, I leapt at the 2015 A3 when the TDI version finally arrived.
I’ve posted extensively about my A3 TDI in other threads on this forum, but suffice it so say that I like it very much. The 12-way adjustable driver’s seat cured the back support problem nicely and without recourse to kitchen towels. Last Sunday I drove to New York and back, nine hours of driving in one day with no discomfort, something which would have been impossible in the Jetta. Eighty MPH is a relaxed cruising speed and I really appreciate many of the luxury features, like the much more advanced navigation system. The biggest downside compared to the Jetta is visibility to the sides and rear quarters. I highly recommend getting the Driver Assistance Package which includes blind spot monitors as well as a backup camera and parking sensors front and rear. Even though the overall feel of the Audi is more solid than nimble it’s actual performance is probably about the same as the Jetta’s and it’s all too easy to be in flashing blue light territory before you realize it.
As for maintenance costs, the Audi may actually be cheaper to run. True, VW gives you the 10 and 20K miles services for free, but then you’re paying every 10,000 miles and there’s a whopping big hit of around $500 for the DSG service at 40,000. Audi gives only one free service, at 5,000 miles, but I bought the Audi Care package for $810 that prepays services through 45,000 miles, including the DSG service at 35,000.
So, those are of the comparisons that are most important to me. Is the Audi worth the extra cost? After owning and driving both cars, I’d say “yes” - for me.