The purpose of 2007's The Best of Chicago: 40th Anniversary Edition -- the group's second double-disc set in just five years -- is plain in its title: it's been assembled with the band's birthday in mind. It's hard to pass up an anniversary like that, and so The Best of Chicago competes with 2002's The Very Best of Chicago: Only the Beginning, a terrific 39-song set that had all of their hits. In comparison, the 2007 set covers a little more ground according to the calendar -- it has songs from their 2006 studio set Chicago XXX, which the 2002 does not -- but it's ten songs shorter, a compromise that might bring it in a smaller minimum suggested retail price, but doesn't really serve anybody looking for a truly comprehensive compilation. For those listeners, it's an easy decision: stick with the 2002 Very Best Of. For those listeners who want a double-disc set that's just slightly cheaper, this 40th Anniversary set will suit them fine, because it does have all the big hits -- so many that it takes a close comparison of the two track listings to realize what's missing on this one.