I've never been a fan of using sqeeze bottles for nasal irrigation. Well, forcing water up your nose, that is. Too easy to shoot water up there and possibly have it go somewhere or do something that it otherwise wouldn't go/do versus if you were just letting gravity flow the water through your nasal passages.

My only exception might be for someone who can't really bend over a sink easily, like perhaps someone with back or neck problems. I can't really think of another case where a pouring action may not be feasible.

If you're really congested from a cold and your nasal passages are swollen, forcing water up there would be a bad idea. It's just going to get trapped inside your sinuses because it can't drain out and possibly lead to an infection.