If your 883 is stock, you may want to leave it alone. Homarr's bike has some slight modifications such as better breathing filter/airbox and less restrictive exhaust. In his case, a jet change was necessary to keep the bike from running lean. If you have done some of the modifications listed above, then you should have no problems increasing the jet sizes. A good dyno man and dyno run or two should get your bike to perform at its best.
If your intake and exhaust remain stock, don't change your main jet, it's right. A bigger one would only make your bike run rich and get worse mileage. It might be worth changing a stock 42 slow jet for a 45, though - won't give you any more power but it will be smoother off idle, because those are shipped a little lean for emissions reasons.
If you make a minor exhaust change, like slip-on mufflers, you still probably won't need to rejet because you have the same intake restriction as before. But if you change the intake too, like a Screamin' Eagle kit, bump up your main jet a notch - 160 to 170, or 170 to 180. And if you do more than simple intake and exhaust modifications, have someone with a dyno help you, because then it gets really complicated, and you can make things worse instead of better.
As someone else pointed out, jets by themselves don't change power, any more than a bigger filler hole in the gas tank would make it hold more gas. They just adjust the mixture to be right for your combination of intake, exhaust, heads/valves, etc. What jets you need is determined by what other changes you make to your bike.