I really think either will do. I like the THawk because I flow it before and taught my Dad to fly with one. It's durable, can fly slow when you need it too, turns quickly when you need it too and would work for the area(s) you are describing to fly at. I haven't personally flow a magpie, but I've heard nothing but good things about mountain model planes. The magpie with ailerons will probably turn quicker. I think the THawk is one of the best "bang for your buck" RTF packages you can get and their customer service is top notch (imho).

One other one popped in my head that's a real nice package and that's the Space Scooter by multiplex. This one may be an even better choice for you as it's a great aileron trainer.

http://www.hobbypeople.net/gallery/240028.asp

The Wing Dragon from Hobby-Lobby is another one you might want to look at as well....

http://www.hobby-lobby.com/wingdragon.htm

Best of luck with whichever model you choose as they all will put a smile on your face. [8D]