Not important if you're deaf.
Kidding aside, we can objectively say the n55 sounds better. Does the s55 sound like shit? The honest answer is not most of the time, it sounds decent, but yes sometimes it can fart in a tin can especially at high RPMs. I believe that's due to the wastegate being open? The n55 however is not immune to this effect either, it farts too. Even the n54 did the same. I think the main difference is when neither of them are farting the n55 sounds deeper and full whereas the s55 isn't as deep sounding and tends to be thinned out a bit if that makes sense.
Bottom line, you give up some good harmonics for some serious performance. If that's no big deal to you great, if it matters too much to you than stick to the n55. Just be thankful it doesn't sound as terrible as a 718 and move on.