I'm in the car business, we sell new vehicles and specialize in high line late model used. Part of my job is to buy all the vehicles for the dealership as well as appraise the trades coming in. That said, we've sold a ton of Q-50's and have had great feedback. The Q 50 was just introduced in 2014 so I can't speak to this exact model's wherewithal, but the power plant and awd system have a solid reputation long term. I've had a G35 AWD(similar drivetrain) and have only had to do regular maintenance(0 issues, knock on wood) and it's over 130,000 and 8 years old right now.
What can tell you about Audi's. They're driver's cars, some swear by them and it may even be bit sexier car is some aspects. If you were only going to own both while they were under warranty, it would be a tough choice in my opinion. Since you're going to drive the vehicle well out of warranty I think the choice is very simple.
I think the nicest way I can say it is this; if you were one of my close friends or family members I would absolutely discourage at all costs the purchase of a late model Audi with the intent to drive to 200,000 miles. Older Audi's come in all the time, always with lights on and all kinds of issues that the drivers don't fix due to very high costs and were not talking a few hundred, instead thousands. Don't get me wrong, I've seem some nice high mileage Audi's, but very rare that they don't have a ton of issues going on beyond what made sense to repair and still make any money. I usually just send off to auction. I always worry about selling a high mileage/out of warranty Audi as the customers ultimately will be upset with us or the vehicle. I'm sure there's been some bad Infinit's out there as well, just don't see them very often. Again, if you were only keeping it under warranty it would be different.
Here's our market right now on Q50AWD which is a $48-$57 vehicle new
2015 Premium Q50AWD(non s) 27-28 selling price + or-
2015 Premium Q50AWD Deluxe Tour 31-32 + or -
2015 Premium Q50 Sport Hyrbrid last one I sold was 28900(no nav) with higher miles 38 k or so.
I haven't bought and sold a ton of sports , simply because they bring thousands more than a premium at the sale. I've found we've been able to provide pretty good value in Sport Hybrids, but don't see a ton. If I was pricing a Q 50SAWD premium, I would likely target my retail at 30-32 in a good color. Hope this helps!