Battlecruiser, on 18 June 2012 - 04:16 PM, said:
putting the psu at the bottom of the case results in it being able to draw in cooler air.
and with the psu at the bottom leaves room for an exhaust fan on the top, which is especially nice for custom amd heatsinks, since they like to blow upwards when mounted,
when looking at any case, to determine air flow you want to look at the inside of the case, and try to visualize the air flow, to try and find any potential deadspots.
as far as fans go, I'm a fan of using the high pressure method since I often buy cheap cases, having more air being pumped in than removed means air is squeezing out the cracks of the case, keeping dust out of those areas and potentially insects as well. however with this method you want some fine dust filters unless you frequently clean your computer
anything after this is aesthetics and personal preference. things like buttons, front audio jacks, usb port number and type, are all up to you, and of course don't forget the obvious rice touches like led's and windows if you're into that kind of thing
with all of this said and done, investing in a small air compressor with reserve tank will save you lots of money on "canned air"
A compressor can form condensate(water) and ruin components. Just to be safe I'd stick with canned air.