I've been long attached to Warbird Digest, Flight Journal, and I'll pick up a Flypast issue from time to time. Another good one, which I wish I was subscribed to, is Classic Wings, which always covers topics that other mags don't seem to, and being based 'Down Under', they always have the scoop on all of the fascinating WWI and WWII restorations happening in New Zealand and Australia – which probably have the most interesting restoration projects compared to the rest of the world (P-39's, Kingfisher's, Mosquito's, P-40C, P-40F's, A-20's, P-38's, Razorback P-47's, Japanese Tony's, and fully accurate reproduced WWI aircraft and engines, led by Peter Jackson).
I used to be a happy consumer of Warbirds International, but I have long since lost interest in the mag, since as long as you check into various forums across the internet, you already know everything that the next issue is going to talk about - which is sometimes similar with Warbirds Digest as well, but it is a better, more well-written magazine, with more insight.