I hate to be so shallow, but unless you're in love with AWD (great for bad weather and awesome for launches), it comes down to image: Wild Child vs. the Buttondown Beast.
The Wild Child always lets you know you're driving a performance car. It's got a lot more road/engine noise and more road feel / engine feedback than the 6. When you pull in or out of a parking space, the exhaust noise makes people turn their heads to see who the upstart is. Give it the gas and the wheel will twitch in your hand just to remind you all that there's a lot of power being through the very same wheels that are responsible for your direction. Take off the DSC and you will lay a patch of rubber even with a relatively mild launch. In corners it feels a good deal lower and definitely lighter than the 6 with 400 fewer lbs to shift from side to side. Visibility all around is better and you can see the road better with the shorter and lower hood. On long trips you better not mind listening to the engine humming to itself b/c there's no putting the sound of the exhaust completely in the background. The size of the two cabins isn't much different in terms of numbers but the Wild Child will make you scrunch your elbow in a little on the door side and your knee will likely be resting against the center console. The back seat will be a little cozy for any adults you put back there with little room to spare if the front seats are pushed back at all.
The Buttondown Beast is almost the complete opposite. It isolates engine noise and road feel substantially and you won't really notice them most of the time. It's only when you really get on it and make the engine roar or pitch it into a corner and accelerate out in full-throttle AWD that the 6 shows it's performance side. The exhaust is pretty quiet and you'll barely get a glance in the supermarket parking lot as you slip in next to the other respectable looking 4-door sedans. Like a middle-class Bruce Wayne, your super powers remain hidden from the masses and only a select few will pick up on the clues to your secret alter ego. Those powers include the ability to launch hard with the just the slightest chirp when you drop the clutch. And you can tell that every bit of the 280 ft/lbs of torque is going directly into forward motion. I don't know what it takes to lay rubber, but it won't be something you do routinely like you do with the 3. On the highway, you can daydream and listen to classical music at a moderate volume if you want since all you need to overcome is the wind noise. Inside the extra couple of inches mean all but the tallest and chubbiest can put their elbows and knees where they want to instead of where they have to. Unlike the 3, adults in the backseat will have the freedom to gesticulate when they talk without fear of smacking the seat in front of them. Best of all, if you're a 30/40-something, middle-aged old fart like me, your wife or serious GF and your clients or co-workers will not ask if you are having a mid-life crisis or hide their faces to avoid being seen in a "starter car" like they might be inclined to do when riding with you in the 3.
In any case, it's a great choice to have to make. I'd love to do it all over again just for the fun of it.