I've always preferred Aeroplane to Flypast. Not that the latter isn't very good; but if I'm strapped for cash and can only buy one then it has to be the former. Aeroplane has always been rock solid, has a great mix of civil and military and very interesting reading. Flypast hasn't been quite so consistant in character over the years, tends to be slighly more glossy, and is just a bit too warbird reliant.
I tend to buy them both whenever I can though, so I guess that must endorse their product!
IM