2.5" would be my choice. Any exhaust restriction reduces performance and fuel economy.

Any muffler can be too loud regardless of the pipe size. With a larger pipe size and muffler, you can reduce the sound level more without restricting the exhaust flow. My car had dual 2" with glass packs that sounded like a machine gun at high revs and attracted police just as fast. I switched to dual 2.5" pipes with Sonic Turbo mufflers and was almost disappointed at how quiet it was. An H pipe also reduces the sound level as do full length tailpipes.

As a point of interest, I ran a single 4" exhaust (equal to dual 2.8" pipes) on a fairly stock Buick 350 4 bbl in a circle track car. All the cars had open exhaust systems and it was the quietest car out there. The loudest? Dual 2" systems. The larger volume has a natural sound dampening effect. And yes, it made more power than the other cars and yes my exhaust was eventually banned!