You'll get better cooling with turbulent flow than with laminar flow. Pulling air into a space guarantees the largest amount of nice, smooth, not terribly effective laminar flow. Pushing air into a space, or, more exactly, onto an irregularly shaped surface or structure, gives you turbulence, which gives you better cooling with exactly the same fan.

Also consider that components with an "up" might not cool well at all when placed sideways. One previous side, now down, will cool best. The side that is now the "up" side will cool least, receiving heat from adjacent and lower areas.