I recall a comment somewhere by Galen Rowell either on the 24mm or the 20mm. The extra stop made the lens bigger, heavier and more prone to flare. For landscapes, it doesn't buy you much anyway, as you are more likely to be stopped down. What is the application you have in mind?
2.8 to 2.0 is a full stop. I have a Nikkor 28/2.8 and it is a wonderful lens. I'm sure the quality of both are equally good. Only you can decide as you know how much money you have available vs how often you would need the extra stop. You could always use faster film but again only you know how large your prints need to be. If you asked me get the faster lens as it is not my money. I know this isn't much help.
"When elephants fight it is the grass that suffers"