Depends on the situation. I like a girl that dresses appropriately for what we are doing. If we are hanging out in a park, jeans and a t-shirt make way more sense than heels and an evening gown. If we are having a lazy morning, boxer shorts and a tank top are appropriate. But if we are going out for a three course dinner, boxer shorts and a tank top would... not make me happy, let's just say...
A guy may be slightly intimidated if a girl is more dressed up than they are at the time, because if they are together in a place and time, they will be obviously being judged as to what is appropriate attire for that specific time and place. A guy in a suit and tie and a cocktail party is not going to be intimidated to talk to a girl in a nice dress with her hair done. A guy in shorts and flip flops is not going to be intimidated to talk to a girl in a sundress if they are both at the beach. Or, rather, won't be any more intimidated than they normally would. The clothing will be irrelevant.
I don't really think the dresses I like on girls are "Dressed up" material. There's nothing better to me than a girl in a sundress or just a cute everyday dress, especially if she's got the legs for it. Jeans are great if they're NOT tight. I hate jeggings, leggings, and yoga pants because I want the body to be a mystery at first and something that only I get to see, kind of like my prize for catching you, you know? I don't want a girl that puts it all on display for the world, I like modesty.
I beautiful woman stands out no matter what she's wearing. Different places and occasions call for different style. I'll be more impressed by the fact that she dresses beautifully in stead of what she really wears.
In my opinion, a girl that wears leggings and a low cut shirt shows me not that she's a slut, but that she has the confidence to wear that. It also shows that she's fine with guys hitting on her or looking at her butt. So I like girls that wear that kind of stuff, but sometimes you have to dress fancy.