1. You might not get any special cards or be disapointed- and selling on may be difficult. However at the same time the thrill of opening them will be fun!~ Oh and they'll end up being put away and not being seen every day like the calendar~
2. You use is as a monthly poster and sell it on later or if it isn't worth much- keep it as a poster (or cut into multiple ones~) and switch as desired~~
Though a calendar lacks the excitement of getting random(??) photos and maybe rare cards in the other two...
3. A book of various members and the shots, judging from their last travel book, are very fun and varied photos and unlike regular, quite staged, solo photobooks~ Plus they'll probably come with a couple of photos and you'll get the fun of the two bonus photos and maybe get a Rena one!
Buuuut~ Books get put away and aren't always flicked through day to day- whereas a calendar will be on display to see every day~
I can't tell you which one to get, but those are my thoughts on each option!