Changing from the stock airbox to anything will require jetting changes of the Bings to have them work anywhere near correct. Those German boys actually spent alot of time tuning the airbox volume, plenum lengths, etc. to the exhaust capacity and pumping throughput of the engine pretty well to the jet sizes and needle positions - if you try to change the airflow, especially on a CV carb like the Bings, you'll have to compensate in other places along the line of the system.
The slide Mikunis are possibly less "interactive" in their operation with changing the wavelength/impedance of the input airflow, but they do come with their own quirks in the airhead application. Usually they are used by guys/gals who are looking for increasing peak HP at high RPMs. Many people find that they have difficulty balancing out having them running too lean at the high RPMs (which can be both HP limiting and contribute to cylinder overheating) or running too rich in the midrange (which can actually make throttle response more sluggish where you spend more of your time on the street), though changing jets, slides, and usually exhaust systems can eventually be worked out.
I ride my airheads on tours and encounter dirt roads, rain, snow, dust, etc. The pods filters don't do nearly as good a job at keeping crude out of the carb and engine as the stock filter box does, and if you're caught in a heavy rain with pods or stacks you're liable to suck a bunch of water in and stall the engine, so I keep my air/carb setup stock (though I would play with jet/needles positions of the bing carbs if changing exhaust systems).
So, depending on what you plan to do with the bike, I'd consider it carefully as it can be a tedious process to work out.
