I also think a softer tip is better (for me) when playing one-pocket. There are a lot of times where you have to shoot really soft and put a lot of spin on the ball at the same time. For me, I am much more confident in shooting those shots with a softer tip.
Like many have said, it doesn't matter. Use the one you're used to playing with.
One Pocket appears to be a softer, slower, game. That is an illusion. It contains all of the elements of the other games.