The way that I see it, maddad pipe is good for someone who wants to keep the stock muffler and down pipes but wants to minimize drone and have some other gains especially more aggressive sound vs stock. This is so because maddads are simply louder than the N55 mids. On the other hand, since there are merely two real differences between maddads and N55: price (maddads are double price) and sound (discrete but still deeper with N55, quite aggressive with maddad), I think N55 are a meaningful choice for someone who plans to add an aggresive sounding aftermarket muffler and/or down pipes too. You won't notice difference between N55 and maddad in that case, not much anyway, muffler will dominate the sound characteristic.
All the other gains should be very similar since they are both non-catted resonated quality pipes with stock N54 pipe look-a-like shape and identical in piping size.
Having said that if I would have the chance I would probably put maddads on my car and it would probably be even louder than it is now, but I doubt I would complain since I show signs of progressing addiction
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"The mark of a great car is one whose overall competence exceeds what you should expect from its individual components and the 1M does just that", Chris Harris.
BMW 1M-SOLD-: TECH: Evolve Race+N55mids, Evolve IC, Michelin PSS, ER cp, aFe filter, CDVx, Vorshlag camber plates, BMS OCC EXTERIOR: trunk spoiler, blacklines, black grills, IND goodies INTERIOR: Alcantara steering wheel, steel pedals, custom mats, MPower e-brake.