I kinda think that both Sasuke and Naruto are masculine in completely different ways. Naruto seems masculine because he is more boyish,cute, and acts more like a teenage boy. On the other hand Sasuke seems more masculine because he is cool, collected, more dominant, and more hansom in a grown man sorta way. But (for some people may have noticed) both Naruto and Sasuke sometimes switch masculinity wise. Naruto can sometimes be a grown up and show his cool sensible side while Sasuke will tend to get moody, whiny, and think that the whole world rests on his shoulders (figuratively).