I'm more of a rational thinker. What do you need? If you are keeping the power below 500hp, then you don't NEED 5". I have a 4" exhaust but have a 5" tip. Looks great!
Do you want noise? You'll have to lose your DPF, kitty, and muffler. My 4" kit killed the kitty, and the muffler is straight through. Nice quiet rumble unless you step down on the skinny pedal. No annoying drone at highway speeds.
If you are only in it for looks, the main part you will see is the tip(s) anyway. I believe you can get pretty crazy on the tips for all kinds of looks. Of course, then there's STACKS!!!!! Hope this helps.