[jwblack750]

Funny, because we have both cars. My wife drives a '14 435xi and I have a '14 640xi. I love, love, love the 640. The 435 feels more like a sports car, and it sounds better, imho (but, I think the '15 640 comes with the performance exhaust standard).

Here's my general opinions:

Fit and finish: Hands down 640 winner

Sporty feeling: 435

Acceleration: Seems pretty even, but I have a JB4 in my 640

Cornering: 435, but the 640 handles surprisingly well

Cool factor: I feel like a million bucks driving the 640, and it gets tons of looks

Trade-in risk: I would definitely want something different if I had a 435 for a while, but I feel like I could drive my 640 for a decade and still be thrilled to get in it

Cockpit: Seats in the 640 are amazing, and you really do feel like you're sitting in a fighter jet or something

Wife's thoughts: She thinks my car is awesome, but she prefers a smaller car, and she thinks my car feels huge, which it kind of does

I'm not a very technical car guy, so I can just give you the subjective thoughts above. But, I think it comes down to whether you are more interested in the driving experience or the aesthetic experience. Feel free to ask any specific questions you have.