I'm not a hood expert, Viggo, but Canon has trended towards simplifying some hoods to only optimally block sunlight only at the widest FL of a zoom. That allows them to make a smaller hood.
A good example of this is the 24-70 f/2.8L (original version) vs. I believe every 24-whatever L zoom that has come since. Taken from TDP:
"The 24-70 L II is nicer to use with the much smaller Canon EW-88C Lens Hood (included) in place and it stores more compactly. The lens is also much easier to grasp with the hood in reversed position. The downside is that the 24-70 L II's hood only properly shades the front element at 24mm. A much larger hood is needed to shade this lens at 70mm."
Compare and contrast -- new version on top, old FL on bottom:
http://www.the-digital-picture.com/Reviews/Lens-Product-Images.aspx?Lens=787&LensComp2=0&LensComp=101
(in fairness, the original version extended out in the
opposite of the zoom direction, so 24mm is oddly the
longest form of that lens.)
So if the internally zooming / non-housing extending UWA lenses are similar, it would appear to be a classic tradeoff -- smaller is better for packing, allows more access to the lens' features when reversed, and is more likely to come along in your bag as a result. The downside? May not block the sun so much.
(I'm waiting for a proper hood / FOV scholar to answer your question, though. The 24-70 original version I referenced is -- admittedly -- and odd duck to use to answer your UWA zoom question.)
- A