It depends on the girl's hair in my opinion. Some girls look really good with curly and straight hair while others look better with straight hair rather than curly hair. Me personally I like both just about the same depeding on the girl. Overall I'd say it's a tossup just go with which hairstyle you like better because when you like the way you look you'll have more confidence and that's more attractive to me than a hairstyle. =)
What I mean is that if you are comfortable and one hundred percent confident with what ever look you are going for than its extremely attractive. Its easy to tell when a girl is trying to hard to a certain look and its a major turn off.
i'd go wavy, curly, its just more sensual. not frizzy curly/wavy though. curls are more interesting and I'm assuming that curly/wavy hair is the type of hair that catches the eye easiest and fastest. I like curly
Straight is preferred by guys; it's said to be the most preferred hair type, followed by wavy then curly :P
Straight is just sexier, often times healthier, shinier and they can run their hands/fingers through it. All of the girls they find sexy such as Megan Fox, Miranda Kerr, Scarlett Johansson, Eva Mendes, Mila Kunis, Lauren Conrad, Jennifer Lawrence-all have straight hair
My hair is naturally straight. At one point I did want my hair to be curly but my family and friends said it just wouldn't be me they said it would be better to leave it striaght so I prefer straight hair.
Personally I like curly hair because I think it gives me a softer look than when I have straight hair. I naturally have curly hair and think it looks better than when I straighten it. Also I am Asian, and most of the Asians I know have straight hair and it's nice to be the unique one without straight hair. :)