I went with aFe, and couldn't be happier. I've yet to dyno it, but the power gain can be felt immediately.
The install literally takes 5 minutes, and needs only to tap into two connectors/sensors.
Lastly, fuel economy has improved. I'm on my second full tank since installing the aFe unit, and I'm getting 30.5mpg avg across both tanks (actual measured at pump) in SPORT mode vs 29.6-ish stock in COMFORT mode.
E90 M3 6MT AW/FR
RAYS | Akrapovic | Evolve | Stoptech | Tecnocraft | Arkym | Swift
'12 F30 328i AW/Blk 6MT
'03 E46 M3