Personally think that N20+8 speed is a pretty darn good combo. Unlike the N55 you actually have to rev that 2 litter to get most of the power (though it does have very good torque very low in the revs as well). It may not feel like its accelerating fast but it's deceptive, I bet you you'll be looking down at the speedo after a few seconds and be surprised at how fast you are doing. I know the first time my wife got in the driver seat and pressed the pedal to get on the freeway I almost spilled that coffee all over my lap from the acceleration that surprised me from the passenger seat.
I actually do like the dual personality of the 28: feather the gas and it drives almost like a diesel and never goes above 2000 rpm, mash the pedal and it feels like a very linear fast four cylinders... And you can't really feel any turbo lag either.
But if you like the instant torque of a 6, you will need to adapt a bit to the 8 speed kicking down the speed very easily and having to work the engine in the revs a bit ... But in the end you will probably be just as fast.
Sound-wise however it's not contest win for the 6, but then again the 4 has the upper hand in gas mileage...
Either way its not bad with ever way you decide to go