As others have said it really comes down to personal preference .
I am very happy with the Akra and like it's more subtle sound profile as it doesn't draw as much attention when driving in the city.
It seems the other option is the Eisenman or Supersprint which are louder and more "aggresive" but both are great exhausts. I had an Eisenman on my X5 and loved it.
All of them preserve the OEM look (to a large extend) and with the Eisenman/Supersprint you could also powdercoat the tips black be even more subtle .
Not sure if it's of any use but here is a short video of idle after startup with the Akra