Sometimes it isn't about volume, or even performace. It is about getting a nice rewarding tone to the exhaust. I've seen/heard a lot of ratty sounding bikes and cars (too many V-twin bikes and Ford Mustangs to be specific) that have loud exhausts, but sound like crap. I went for tone, not volume. If the stock exhaust had the same tone as the exhaust I got I wouldn't change it, but it didn't.
I also contacted the manufacturer about ECU management reflashing. They said none was necessary. Figure if anyone would know the manufacturer would. Maybe a bit could be picked up with a reflash, but I doubt I'd really notice it anywhere but in my wallet. Plus it seems a majority of the time the reflash costs mpg. Doing around 55 mpg, I'm not getting the ECU reflashed.
FWIW I like the old school long exhaust, so I went with the Delkevic with the 18" can, probably would have done fine with the shorter 15" can with the baffle they come with. I also got the quieter core in case it was too loud, since they could throw it in the box with minimal shipping cost as opposed to having to order later. The tone was excellent, sounded like a muffled Yamaha DT-07 flat track bike. It also wasn't overly loud either. I got a dB meter ap for my cell phone and did a check at about 24" and an angle of 45° from the tip, getting 87dB at idle and 96 dB at around 6000 rpm (sitting still).