If you go for midpipe only + cobb it won't matter much what pipe you take in my opinion. More a matter of taste/budget. I have a Miltek midpipe + Cobb with GTC custom tune and the difference is very dramatic. If I will upgrade to a full Ti system I will go for Akrapovich. It gives a little power gain vs most other systems although really not worth the money. So thats more about sound and taste as well. And being snobbish. As for service, both GTC and Miltek are absolutely great.