both are greatly over-rated, although there are some decent DIY in pop mech. There are quite a few easy to read magazines out there that I'd recommend well before pop-science. Discover, Scientific American,...
The only time I wish I subscribed was when I'm at home and have to, uh, use the bathroom for more than 30 seconds. (need some reading material!) Otherwise, my school's library has several worth reading, and I have access to subscriptions online via my school for dozens (hundreds) more. I could pick up the popular science in the library, but I've found that quite often, it's not worth my time. It's too... sensationalism?