Cooler master HAF XB:
Judging from images online, this case has decent airflow capabilities as long as you add more than the 2 fans included. There are many ventilation holes, especially if you choose the one with the mesh top panel instead of a window panel. However, it seems most ventilation holes are not dust filtered, which means dust could build up fairly easily.
Corsair carbide 500r:
With a total of 4 fans, 2 at the front, one in the back and a 200mm one at the rear panel, airflow probably is the main strength of this case. It is spacious and has some dust filtering (the front fans are covered by a mesh and there is a dust filter at the bottom.
Personally I like the 500r a bit more, but it has a lot to do with the case shape and design. As far as airflow and dust are concerned, you won't have any issues with any of the two but the 500r has better dust filtering.