High Flow Cat, what size?

[bigbirdSCed]

so 3 bad cat codes in a row and slight power loss has driven me to decide its time to replace the OEM cat with a magnaflow high flow. but im courious which size i should go with or if it makes a difference. the price difference is minimal so thats not a concern. im ultimatly goin with a 2.5" exhaust. so my question is whether a 3" would flow better then a 2.5". the 2.5 would be easier to mount but if i can have the same emissions passing effects with the 3" and have better flow would it be worth fitting that?

[Midias]

2.5