There are quite a few threads over the past year on this subject. Just do a search for side steps. Mostly it seems a matter of personal preference. After reading all the old posts I went with side steps and I like them. They are functional and I think they look good.
I have the side step installed on my MDX and I am not as happy with it as I was with the running board on my explorer. The running board is a bit wider which I seem to like better. Sometimes the side step is a nuisance because it is so small. I think it is based on preference.
It is definitely a preference issue. I have the Acura side steps and they are perfect for my needs. They don't protrude too much, so that I can simply step over them when entering and exiting the X. My kids make use of them and are useful for retrieving the baby from the carseat.
I have the black Maniks on my white X. I really like the looks of these side steps on my X. I thought the Acura side steps did not offer enough stepping surface. And they also cost twice a much as the Manik side steps.
You can see some excellent photos of the black Maniks on a silver X taken by gto-dave in the gallery section of this website. I think the name of the thread is : Zaino...(sorry I don't remember the rest of the title).