I reccomend the soft versions. why? with the soft cover versions they are cheaper, for starters. Also, many of the soft cover books have better pics, in my opinion. I like some of the soft cover cover pics better. I think you should by all the soft cover ones frst. then think about possibly getting your favorite volume in hardcover also.
I bought the first volume in hardcover for collectable reasons, and plan on getting the 6th one in hardcover too, even though I have all 6 del rey manga in soft cover. ^.^ obsessed.