With a WA zoom, you can more or less frame and shoot from a fixed position, or with considerably less moving about. But this does not bother me. With a UWA prime (on MF) I routinely move around anyway. And 17mm is quite a darned tricky view to manage; of the 400 Ilfochrome Classic prints produced from several lenses, only one was printed featuring that 17mm end, and it worked a treat, in the right conditions at the right time. It's a very good size for open landscape photography but it must be balanced with a very strong foreground anchor or lead-in to keep the perspective balanced. I apply that rule anyway with either 45mm or 55mm primes in MF. I think 16mm is too extreme; the happy medium seems to be in the 20mm to 45mm range rather than trying to take in the whole world before in an extreme wide angle view on a relatively very small frame. You could look at zoom vs prime (I maintain that the optical quality is top notch for many, many zooms now, on a par with primes) as coming down to preference based on experience and the end product (large prints where optical refinement will clearly be on display), not assuming that what is suitable for one photographer will be universally suitable, good and proper for another. That said, I'm not going to pan Canon's fine 17-40mm (I also have a 70-200 f4L tele-zoom with equally refined optical pizazz), just that I do not use it (or 35mm) so frequently now.