Hi there!
The DA14 and the DA10-17 are both great performer, but each one is some kind of special...
The DA14 ist good even unter low light conditions, see my examples below. But it's not a lightweight. It was my most used lense last year and was perfect for nearly everything
(macros, landscapes, architecture etc.)
But one day the DA10-17 arrived and everything changed, because the 10-17 ist my new love.
It's very sharp even wide open and it's fun to play with it.
One thing is important using the fisheye, you have to learn how to handle the distortion and
to use it the right way otherwise the fisheye effect gets boring. With the DA14 you can get
very close to objects, but with the 10-17 you can get even closer and that's really cool.
If you own a 16-45/16-50 you got "normal" wide angle @16mm, what should be enough at
most situations and the DA10-17 would be a nice to have. Without a good standard-lense
starting @16mm the Fisheye ist not the best idea.
btw.: I sold my DA14 some days ago
Some examples with both lenses:
DA14:
DA10-17: