Eh... Quest has been hit or miss. The print quality is consistently, well, crappy. No color photos, and frequently lousy photo reproduction. They have run some pretty good articles in the recent past, however, after a long slump.
You'll hear a lot of opinions about Spaceflight. I give them credit for good photo selection and quality. Layout is boring compared to mass market magazines. As for the articles, it depends what you like. I've heard a number of complaints about them running travelogues of ISS missions. But they've had some interesting stuff in the recent past. For instance, last year they had an article where somebody tracked down all the remaining Saturn F-1 engines.