i was going to get a 3 inch random tech cat a 3inch in 3 inch out magna flow muffler but i cant find anyone in nj or va to do mandrel bent piping only crush bent so is it that bad if i got with 2.5 inch cat and 2.5 mandrel bent exhaust

basically 3 choices
1 buy 2.5 inch cat and 2.5 inch mandrel bent exhaust somewhere bought from some company

2 3inch random tech cat 3 inch in out magna flow muffler crush bent 3 inch piping

3 if someone can tell me some who does mandrel bent piping

whats better crush bent 3 or mandrel bent 2.5
and is there a real difference between 2.5 and 3 inch piping