Hi Julius!
When you say Korean I guess you mean Kia 
I see no reason to buy one. Then again, I see no reason not to 
However, I see you talking about VW and Audi... those are big "no-nos" in my opinion (because, like I said, I value reliability very much). I don't know why you say they are very reliable... According to pretty much every statistic I've seen, Audis are up there with the most unreliable cars there are. VWs are average. According to personal experience, I've had a VW Golf IV (my first car) and it had problems with the electric windows (like every other VW Golf IV) where the window would just fall into the door and leave the window completely open (so an immediate trip to the garage necessary), and I also had trouble with the MAF unit, like some friends of mine with the same engine block. Since Audis, Seats and Skodas all share the same engine blocks, I would steer away from all these brands.
My parents like BMWs... also problems. My mother with her brand new X5 had trouble with transmission, right after a few weeks with the car. Yeah, they took care of it as it was under warranty, but it's still not very pleasant when you need your car to go to work and they didn't even offer a replacement car.
However, if what's important for you is top interior quality and comfort and security (both active and passive), then yeah, German cars
I drove my mum's X5 and the thing is just unbelievable. I had a 3-series coupé at the time, which was already quite nice in my opinion, but when I tried the X5 I was blown away. The thing will simply stay on track, no matter what dumb things you try to do with it And from what I've read, the Porsche Cayenne is even better, so I can imagine that in terms of safety and performance you couldn't have chosen better! I wonder if you've had any mechanical problems until now though? I'm working in Germany now... when I talk about this most people say "no no, German cars are the best!" Then I ask... ok so what do you have? Usually the answer is Audi or VW. Then I ask... ok so your car never needed repairs/replacement parts? And the answer most of the times is yes, multiple times
So, to sum it up, if you prize reliability, I would go for Japanese, you can't go wrong there. If you prize quality/details, performance, safety (and a little fun), German, but you pay for it, and you should be willing to have the car in the shop every now and then. I see no reason to buy other cars (except Italian for the supercars... I don't think they will ever be for my wallet though 
, unless I go freelance sometime in the future...) 
Cheers!!
Bruno