Since I just went thru this I will share what I know.
Being from the great north,and a smaller center sort of limits availability of stuff but in the past I've put FloPro exhausts on my V8s and liked them.
Performance shop here had a 4" cat back system for the EB so I thought what the heck....a year of living with my EB wanted to change something.
Kept stock system just in case.
So on it went.
Must increase air flow cause truck acted goofy for a while then ran good.
It's a frickin loud system,with a lot of drone,especially above 2000rpm.No way on earth I am going to pull a trailer with this.So back to shop looking to put a resonator on to get rid of drone.He has a Flo Pro part he thinks wil do the trick,on it went.
Initially I was disappointed in the result,thought it quieted down the exhaust note too much....but did get rid of drone.
Decided to make a video of it to see how it sounds and was pleasantly surprised at it(I'll post vid when I get to my computer)
After driving a month with the extremely loud system made the resonator system seem quiet,which it really wasn't.
Long story short....I wouldn't even think about a system without a resonator in it.
People are going to have to accept that the sound the EB makes is going to be unique..if you want V8 sound buy a V8.
People have said mine sounds almost mini diesel ish....I'm good with that.
As far as performance goes the dyno says they make a difference,I think it holds gears even longer and has more snap....but whatever.
I wanted a bit of exhaust note,added performance is a bonus .
Leave it stock unless you are willing to tinker a bit and accept it will make noise different than anything out there.