if you dont mind blowing some money, eisenmann sr mid pipes and meistershaft touring muffler is my setup, and it sounds phenomenal
definitely louder than performance exhaust and most of the common exhausts I have heard on e90's but its a really refined sound.
I have yet to hear a muffler delete in person though so I can't compare to that
Current 07 BSM E92 335i
Previous SGM E90 330i (R.I.P.)