A fundamentally confusing debate with a focus on lexis, I think that being stylish involves having a style identity whilst still being perceived in a positive manner. For instance, if I were to dress completely head to toe in tiger printed lycra, I would have a style identity (per se) but I wouldn't be stylish. Whereas being in style means conforming to the trends and conventional fashion as it comes and goes, what is known as fast fashion covers this area greatly. Although this explanation is waffly and confusing it is the best that I can do to sum up the distinguishing factors between the two aspects. (Sorry I've never been too good with words).
Truthfully though, it is all subjective.
I am sad to say that a lot of street style has become quite conventional, in that gone are the days of the great differences in style in subcultures ranging from teddy boys, to goths, to rockabilly, etc, etc. Although you will find a few areas where the street style and subcultures are still prominent, such as the Harajuku girls of Japan. Many designers and fashionistas take elements of the subcultures and incorporate them into fashion nowadays (see teddy boys creepers), but in a much less concentrated way -see Dame Vivienne Westwood for one of the more true-to-form examples of punk influence. (In my opinion) these people therefore become 'stylish'.
But what has become of the beloved pioneers of fashion is a diaspora of their distinctive styles.
Unless stated otherwise,
all pictures were found through images.google.com
It makes me sad that people aren't more adventurous with fashion, but I am also a victim of this wave of conventionality (fear of being too individual, though there really should be no such thing). Unfortunately, the way that people (generally) perceive the world is with the view that although we wish to be different, we long to be accepted and that means to be the same.
I think we should all take a page out of the books of these fashion icons, and learn to be more accepting of all styles and fashions, because individuality should be valued over conventionality. Let's start an identity revolution; be who you want to be, because at the end of the day, who the fuck really cares?