I happen to be partial to the OEM exhaust in the looks dept, and the factory apparently has done a decent job of designing it, when you look at what happens to the people who think that the Cobra 4-into-4's are a performance enhancement.
There were few years using the black chrome, yes, they're rare, as to $$ value, like anything else, it's what someone is willing to pay. You can price the OEM exhaust and see that new is a very-expensive proposition. That's 'if' the black ones are even available anymore. I'd say that for someone who wants to buy or obtain an OEM exhaust and has a Kerker 4/1, they will lose some RWHP, but return to the stock appearance, which I think the factory got it right, the first time. For the fellow installing the Kerker 4/1, and with proper re-jetting, you're going to see a decent increase in HP, and the sound at idle, 'bragging-rights' at your local bike night. The youngsters will be surprised. "
What's that sound? You got cams in that?"
"Why ye, yes, I do!" Otherwise how would it run?
Be aware that you will have to remove one of your centerstand mounting loops, and probably either grind or try to bend the other, to mount the Kerker 4/1.
Something that could make-up your mind, ride the two, back-to-back. See for yourself what the difference is in throttle response and top-end. If the friend doesn't have the Kerker installed you just have to go then, 'on the literature,' which says that you should be able to gain about 10% from a proper swap. A 1300cc Venture engine and a Kerker 4/1 would give you a good relatively less-expensive power increase. You'd probably be making somewhere between 120 and 130 RWHP.