2011 has this epic extended laser-light intro where they're dancing in a way that makes it look like they're moving the lights around. Reni-chan also gets overwhelmed during her intro and bursts into tears, adorable.
2012 does a similar laser-light thing but there's this monster dude in the background that
Spoiler:
turns the girls into middle-aged chubby men during kaito shoujo
and the audience needs to chant loud enough to get them back. 2012 also has my favourite Reni-chan magic show.
2013 is a way bigger concert and those animal costumes they wear are one of my favourite costumes of theirs.
Personally I'd buy them all and miss a few dinners, they're all so good =P.
Thanks for the suggestions nemurenatta and dmk! I might have to just get them ALL! Think I'm gonna go with 2013 one first in order to not break the bank.
Got confirmation from CD Japan the new BD has been shipped and will be delivered tomorrow. :)
^ Probably a lot. The search function on Hello Online sucks, sometimes I have to use google because I know that a torrent exists on H!O but their seach is not able to find it. Not even when you search for the exact title, it's ridiculous.