I'm going to agree with seri here - if I man takes care of himself and is well groomed then it makes no difference to me if his hair is long or short. Certain hairstyles tend to be more flattering on folks with certain facial features or shapes, so case by case basis there.

As for hair length being more masculine or less masculine? Time and culture adjusts that outlook on a pretty regular basis so completely moot point as far as I'm concerned.