Hm, tough choice. Soft cover is cheaper, hard covers will cost an arm and leg most of the time. But with hard covers, you can open the book as wide as you want without fear of creases to the spine (I hate that when it happens to my soft cover books, the reason why I usually don't let anyone touch them). In the end, I prefer soft cover since I'm pretty kedekut wan... But I'll go for hard cover if the book is really special/cheap for a hard cover/some one 'sponsor' me.