Then there's always this: Men's clothes allow free movement. They can be purchased in a size that's reasonably close to what our bodies really are, are usually from non-chafing or clinging fabrics, and can be worn in a variety of settings instead of having a different "outfit" for every event.
In short, men's clothing is more sensible.
I generally wear women's clothing (mostly because I am well-endowed, so men's shirts don't fit), but my wife prefers men's clothing. It's not so much that she can't stand "girly" styles, but she's outdoors a lot (research scientist) and men's clothes are made better, cheaper to replace, and more comfortable and versatile for what she's doing.
As for the haircuts: This too is an issue of convenience! If you like (or are willing) to spend 40 minutes every morning making your hair look perfect, more power to you! But the real advantage for short and simple (i.e., "mannish") cuts is that you wash the hair in the shower, dry it, maybe run a comb through it or a little gel/mousse/wax, and go.
When two women are sharing a bathroom, it helps to cut down on time spent primping.
Oh, and have you ever considered that most of women's primping is done to please/attract men? And if you're not interested in either pleasing or attracting men, you can save a whole lot of time and money for other things.
Basically, don't think "man-like." Think: sensible, comfortable and convenient!