I've used everyone of them. There are none that come close to unreal Book.
The only other one I use occasionally for a totally different application wich I like for other reasons is Gig Book. But Unreal Book is untouchable and cheap!!!!
Mikey, You've made some great recommendations thru the years and unReal book has to be right at the top. imho, has to be the single best app and most useful that I have on the iPad.