Well, for one thing it changes the uniform look of the albums. Just look at how different a shelf would be.
You're going from one look to a different one after 58 albums. One positive I see is that it's easier for kids to take care of. Jewel cases aren't always durable, so the cardboard switch I could live with. The weird thing is they are supposed to be doing 2 of these smaller albums in a year. But, with the way they are releasing things months in advance to OAC and then radio 4 months later, I don't see how they will cram 59 and 60 into 2015 unless they release 60 to OACers while 59 is on the radio.