I'm also interested in why people change the Scrambler's exhaust (waiting for August delivery). I've only had 30+ year old bikes and don't have any experience with roaring engines and performance tuning.
Is it sound, power, or fueling that's making people jump? Seems like a high percentage on the forum have bought the race Termignoni immediately or installed on delivery.
There is no doubt that uncorking the exhaust has a few benefits. The question is more whether or not those are meaningful enough to you to spend the $$$:
1) Weight saving: Most aftermarket pipes lose the catalytic converter (heavy) so you're effectively shaving off a few lbs from an already light bike. Does that make a significant difference in day-to-day use? On its own, probably not. With other mods, power gains etc...maybe?
2) Power: We're talking small gains (2-5 HP at the wheel and comparable torque on this bike) but may be a factor for some. Worth noting that Termi solutions will be the only ones to come with their own re-map/ECU so fueling and power SHOULD be as good, if not better than stock. Other aftermarket pipes do not come with an ECU remap so it's up to the owner to decide if a remap is required (subject of this thread) or if they are happy running stock mapping (in most Ducs that use this type of motor from years past, fueling at low RPM does degrade by doing slip-on only and no remap and I would assume that it's going to be the case with the Scrambler). You also get into existential questions here, such as "does this bike need more power?" (and the answer...well, it's pretty much always yes
3) Aesthetics: Subjective, but also a factor. Shotgun, under-seat, high pipe, etc
4) Sound: This one, to me, if probably the most significant reason for switching to aftermarket. Losing the catalytic converter usually makes the bike louder, then, depending on the pipe design, will also modify the sound (growl, shriek, purr...and everything in between). A bike that sounds better may "feel" faster...whether or not it's actually making more power is another story. Motorcycling is a visceral experience so it's no surprise that most Ducs end up with aftermarket pipes at some point.