[m630]

Hi,
Interesting situation you have there, I'll just post some random thoughts for consideration. If you like to change cars so often, I think that a lease is the most cost effective way to go, you have to be taking a hit with the ownership route, either by trading in a two year old car to a dealer, or looking for someone to buy a higher end 2 year old car privately, just not things that I like to get involved in, so Id say look into a lease, it absolutely works out to the same or better financially in every case, imo.

In terms of your choices, I think first you have to decide on a budget as there is a quite major difference between the options you are noting.
The 650xi is very expensive, and the 650 GC will be even more expensive than that, we're talking over 100K nicely optioned out, so consider your budget carefully. Again, if you lease, you can get into these more cost effective, but still, they aint cheap by a long shot.
Unless you drive the F10 550xi and absolutely love it, I would discount it immediately. It is a very very large car, just a tiny bit smaller than the 7er, so coming from an e92 or s4 will be a very big change, the car is massive and heavy. Its quite a bit less than the 6er but thats all I can say nicely about it as I had one for almost a month during some service late last year and ruled it out as a replacement for my car in the coming months.

The A6 is OK I suppose if you want something a bit bigger than you have now and it wont cost nearly as much as the 550xi, and may be a better car, but Ive never driven the A6 so cant compare honestly.

Then you listed the 335xi coupe, now Im not sure if you are aware, but that car is being redesigned and the new concept should be shown this year, but its not coming out any time soon as far as I can tell, im not sure it will be this year, so if you are looking for something to order now, that would not be an option. However, if you start reading up on the F30 335xi sedan, you may find an interesting option especially since you are coming from the A4. The 3er has grown again, and now its basically the same dimension as the e39 5er, so its quite a useful size car and Id now compare it to the A6 vs the 550 which is really big. I find it a great looking car and may just make the move to one soon.

Some other points to discuss if you look at the 6er for example, if you get that level of snow, you would definitely need to put snow tires on the car, and even with that, Im not sure that it would be the most useful since its so low, so depending on your road conditions, that may be a factor.
Ive been driving the 6 series for nearly 7 years now, first in the 645ci and then with the M6 for the past 3 years, and I have a dedicated set of winter wheels with snow tires and I have been able to use the cars as daily drivers with the amount of snow and ice we get down state. But, im not sure you would get the same use based on the stats you noted above, thats alot of snow and probably alot of time when you have to drive in the snow. With all the power, regardless of x-drive and even with snow tires, Id never drive the 6er in a snowstorm unless its an emergency, it just isnt meant to be driven in blizzards if you know what I mean.

good luck