Information on the OVA:
http://www.andriasang.com/e/blog/201...kyria_3_anime/
Seems like you get a mission where the Nameless join up with Squad 7 if you rent the OVA from the PSN, then if you buy the Limited Edition BD you get a mission based around Isara.
OVA PSN release info:
http://valkyria3-anime.sega.jp/delivery.html
BD/DVD release info:
http://valkyria3-anime.sega.jp/goods.html