If your favourite focal lengths are between 35-40, the little 27mm might be right for you. It's small and cheap and people like it. It's a 40mm equivalent. And you can sell it in a few months and buy the new XF23mm F2 WR when it comes out - a small, fast-focussing, weather-resistant 35mm equivalent.
A prime lens is more limiting than a zoom, but that's a good thing. A zoom lets you take the best possible picture from wherever you happen to be. A prime makes you realise that where you happen to be may not be the best place to take a picture from. It makes you think more about what you're doing, and move more.
