I get all three of the big U.S. mags. It cost me about $36 a year for all three, if not cheaper, get em all man, its like getting three presents once a month!
If I had to get one I would do Surfer, thicker mag, way better in the article department and plenty of east coast coverage when there is something to cover. Also they have a great board buyers guide, wetsuit guides, stuff like that wihich is nice to see whats new in the market. Surfer is the king, then Surfing, tTansworld a distant third.
But Transworld gives the best free crap. I got a pair of Sanuk flip flops with a $13 dollar sub to transworld. Just wait for the best free deal things. My Transworld had a subscription card in it last time you get a free T-shirt with a year script.
In fact i got two years of surfing and surfer for $24, thats the both of them for two years. Thas $6 a year for each.