Totally biased opinions:
Guns&Ammo -- Kind of the standard in the field. All around mag, not too technical, average writing quality, fairly accurate, probably biased by advertising.
Shooting Times -- Written with an eye toward the novice, IMO, but with some technical articles. Slightly better than average writing quality, pretty accurate, probably biased by advertising.
American Rifleman -- A mix of technical and non technical. Slightly better than average writing quality, very accurate, probably biased by advertising. A recent format change has made it a bit confusing to read, IMO.
Handloader -- Very technical. Above average writing quality. Very accurate. Probably biased by advertising. Has been headed downhill in the last year or so, IMO, but still the best of its kind.
Rifle -- Published by the same folks who do Handloader, with many of the same writers. Same comments as for Handloader, but bearing in mind that the subject matter is a bit different, as the titles would suggest.
American Handgunner -- Moderately technical (there will be parts the newbie won't understand, but much that he will). Well written, but with more typos than I'd strictly like to see. Pretty accurate, probably not biased by advertising.
Guns -- Sister publication to American Handgunner. Not especially technical. Average writing quality. Average accuracy. Don't read it enough to know how affected they are by advertising.
I haven't taken Shotgun News since it changed from a sales magazine, and I've never read Gun Test but intend to take a look at it after reading this thread.
IMO, the new/average gunner will enjoy Guns&Ammo and Shooting Times more than any other.
I personally enjoy American Handgunner more than any of the others. Handloader and Rifle were my favorites up until a few years ago when they let Ross Seyfried go. Seyfried is, IMO, the best gunwriter around and I still haven't forgiven them.