- Either EF 14mm f/2.8L II USM, or EF 24mm f/1.4L II USM I have never shot with the 14 f/2.8L so I cannot attest to it. However, I have the 24 f/1.4L II and it is fast, sharp, has beautiful color rendition, and an amazing build quality. When I look for a fast lens, this is the one I reach for much more often than my 50 f/1.4 or 85 f/1.8. If you choose the 24mm, make sure you micro adjust it, as it is a notoriously finicky lens.
To me it's kinda like saying, either a 50mm or a 600mm, swinging the 14 and the 24 from the same branch. They couldn't be more different, and they have a VERY uniqe look both of them. The 14 is extremely wide with LOTS of dof, even at 2,8. And very difficult to use for general stuff as you need to put a subject very close to get some depth and impact in the picture. SImply relying on a UW perspective is going to get old very fast, I have owned it, so I know.
The 24 is VERY cool with the pretty wide angle and the very shallow dof (compared to the 14) which is a completely different look. The 24 can be used for millions of things the 14 can't.
If you want the very best wide-wide lens, get the TS 17, it can do whatever, and the 14 can't do any of them. With the 14 I found myself always trying to shoot things dead on, or else you will get extreme converging lines, which you can fix with the TS 17. The 14 is hugely limited lens, but for great landscape photographers, it can make some astonishing, truly epic.
The 24 is my absolute go-to wideangle on my 5d3, wonderful wonderful lens. And tricky focus? No, but there have been a bad batch or two of this lens, I replaced two copies because the focus was all over the place, but my third one is rock solid (thanks to Reikan Focal).
The 50 is tricky focus :oP