They'll all work to some degree or another in different ways.
I've gone the Power Vision route which yes is the most expensive of the bunch but I got it in my package from Fuel Moto when I did a header, slip-ons and a air cleaner. I actually get a little better MPG now than I did when the bike was stock and a shitload less heat coming off it. Would I do it again? Yep, it runs so much better I'd do it again. Do I mess with it, play with the software, etc, etc? No I don't.
If you only do the slip-ons you probably don't need to do anything right away, maybe ride it for a while and see how it goes.
If you do the air cleaner later you'll probably need to add fuel.
I know a lot of guys have had issues with pinging with the stock ECU tune and a tuner (nearly any tuner) will help.