I like the AA x pipe since you can swap the front sections pretty easily.
I do plan to get another AA x-pipe. Buy an extra front section and weld in the OEM cats. Use that section for the street and inspections. Use the straight pipe for the track or whenever it feel the need.
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red