If you want something that takes design on an intellectual level as opposed to an eye candy one, then you need to subscribe to the daddy...
Emigre.
The same could also be said about
Blueprint magazine as well.
Creative Review is a good read, covering the global design industry... covering everything from print design through new media, motion graphics and advertising. Well written editorial content as well.
Formerly Graphics International,
Grafik has really tightened up it's editorial content recently (something that was never an issue when it was Graphics International) focuses more on bleeding egde and contemporary designers, sweet looks as well.
Expensive, but worth the $$$
GAS BOOK offers up a glorious eye candy review of the worlds leading designers and design companies, from the
Shift stable.
Well they're the ones that I recommend...
Out of the list you've given, Design Graphics looks exactly like Digit and Computer Arts magazine, which I stay away from like the plague, all they're concerned abvout is software and eye candy... with no thought behind the conceptual process of design, just how to use the latest version of Photoshop or Illustrator to rip off the latest trends.
If you could pony up the $$ then I'd go for either HOW or Print, both are similar to Blueprint magazine, and put a fair amount of emphasis on the theoretical and conceptual process of design.
But if it came down to it... and you could only choose one, buy Emigre.
