I'm a fan of Akra and I would suggest it because it would be easier to upgrade to a full system later (can add the Akra Evo mid-pipe more easily). Plus there are many available used and it will be easy to sell in the future if/when you move on to another car.
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'13 E92 M3 - Alpine White - BBS E88, JRZ, Akrapovic, AP Racing
'04 E46 M3 - Jet Black - BBS E88, KW Clubsports, Brembo BBK, SuperSprint Exhaust, Recaro - FOR SALE