Definitely long, though too long is just odd looking. If it's too long, it also often doesn't really have any style other than "long," and I like when there is something of a style to a someone's hair. To that end, I selected shoulder length to mid-back. Shoulder length or just a bit longer is pretty much perfect as far as I'm concerned.
Shorter hair can be nice too, but the styling has to be just right and even then it's hit or miss as to whether it suits the wearer in such a way that I think it looks good.