I'm currently looking for a general purpose lens, and I'm more inclined to opt for a prime lens. There are several reasons for that; I want a fast lens and prime lenses tend to be faster at lower prices. Also I think it will be a good way to compose my shots more consciously, as I have to actually move for certain compositions and can't just zoom in and out.
However, I'm not too sure about which focal length I want. I have a Pentax 50mm 1:1.7 which I like, but on my APS-C sensor camera the FOV is not large enough for me in some situations. At the moment, I have the option of buying a used Sigma 30mm f1.4 DC HSM for 270€, which I think is a good offer. But before I buy it, I wanted to ask if anyone has some experience with 30mm lenses (on APS-C sensors) and if they make for good general purpose lenses. I don't need to take epic panoramas, and I don't to zoom in on stuff that's kilometres away. With the 1,6 crop it has a full format equivalent focal length of 48mm, so quite close to 50mm equivalent which as far as I know many people tend to regard as a good general purpose lens.
Is that a good choice? Is there anything I should be aware of (i.e. certain limitations of that focal length)? And is 30mm on an APS-C sensor a good choice for portraits (i.e. can I take frame-filling portraits without too much distortion)?