Aperture:
If you plan on shooting indoors a lot with available light, then the full stop aperture difference between f/2.8 and f/4 could make a difference. Doing a travel shot handheld inside a dark cathedral, for instance, could mean the difference between using an ISO of 1600 and 3200, and on a large print that would be considerable.
For more general outdoor photography a faster aperture on a super-wide lens does not make much of a difference. In most instances, particularly in landscape photography, we are going to want to stop the lens down for f/8 or even more to maximize depth-of-field, a quality in which a super-wide excels.