Princess resurrection production is very similar to Full Metal Alchemist. Although the "parent story--anime" follows the story.. the random story of each episode has no connection what so ever to the next episode. Monsters show up and never appear again. Where the original story is creative but not as great as the manga intended it to be. The story is alright, not too bad. bearable. The ova is way more interesting than the actual main stream anime. Although if Hiro the main male protagonist has some sort of power which allows him to actually save Hime, i think that would improve the storyand increase the poll numbers. But instead.. he can only take shots in the gut and die.

The artwork may not be up to par with the main anime because they tend to make the character's faces longer to try to produce a more mature face although it works for some character..
The art work for the main story is a lot "cuter" than the ova
Also.. in the main anime the producers tend tone down the violence. In the ova the artwork is almost exactly identical, where Hime gives her blood to Hiro to revive him and in the anime they use "Flame of Life"

The music in this ova is a lot better in my opinion. The OST in the battle scenes really suite the character's movements

In other word I liked the ova way better than the actual 25 eps anime.
Give it a try!

Ciao for now!~