The RIOT number calculation is actually the more accurate measure as the formula can take into account the amount of wins possible for the team you are competing against for the playoff bid. Often times the RIOT number is less than the magic number although, as you can see at the RIOT website, the current White Sox RIOT# is the same as the magic number:

http://lyle.smu.edu/~olinick/riot/american_league.html
The website also gives a decent explanation of how the math works and why it often differs from the traditional magic number, if you're interested.