to answer the initial question - how should they fit? if we're talking about road shoes then they should be snug to your feet with minimal room to move your foot when you're all strapped in. extra space in any direction will result in a loss of power from your muscles and body - through your foot - into the pedal. extraneous movement is bad. a buddy of mine actually crams his foot into a smaller shoe than he should take just because he's so anal

if you don't care about loss of power then get what's comfortable. that simple.