Mostly it depends on what YOU want. For example, do you want to display every plane available for a particular airline? A particular airplane in as many liveries as possible? Do you want every inch of display space covered? Do you want glass, or wood? Do you want a diorama? How much acreage to do you have? You get the picture. There is no right or wrong answer, go with what you like.
Even with 1:200 – which are more pricey – there are individuals who collect them by the dozens. You might want to do some google image searches to get an idea. You mentioned IKEA. That is a good starting place for display options.
I, like you, used to collect 1:400 because it was important to me to have a model airport. Eventually, my mindset changed to displaying the planes on their own. I personally chose to go with 1:200 deliberately because of the price and size as it would limit my purchases to something that I really want and need. My recently started display shelving unit http://www.wings900.com/vb/1-200-sca...ollection.html
is perfect for me as I have extremely limited square footage. It will have a maximum of 16 planes at any one time and anything I display over that amount will be done so on a rotating basis.