For the landscape, i would get the 18-105. I would think doing long exposure with either one would not be a problem, but you can get wider open with the 18-105, giving you a bit more light entering the lens. However, you might want to look into a prime lens for landscape - i assume you are doing long exposed landscapes?? Further, don't forget your tripod and remote, these are needed with long exposure shots. Aside from that, i think someone who is a landscape photog will be better able to tell you which lens you SHOULD get.