I've driven the V6 manual and I own an I4 so I can't provide a perfect comparison but based on my experiences, here are some thoughts:
V6:
Sounds better.
Power delivery is more linear.
Slightly more powerful (allegedly!)
i4:
Sounds loud but there's no particular signature to it.
"Feels" faster due to the greater torque from the turbo.
The engine is way more modern and packs a hell of a punch for a 2.0.
There's no discernable turbo lag. Power is instant and it always feels eager - like an NA engine but with added punch.
In Auto the touring shifts are smooth and the sport has a very aggressive map (holds onto gears longer, keeps revs up)
The manual shifts seem responsive to me with only minimal delays (similar to my RS3).
With 8 gears, it's remarkably economical on long journeys, doing 1,500rpm at 70mph. I've seen 35+ mpg
In summary - the V6 wins on soundtrack for sure. Coming from a V8 - I do miss that aspect. Everything else feels like a win for the i4. I can't imagine the V6 auto doing anything else better but someone with an auto should be able to provide some balance here
