Angels are very fun, lower maintenance pets. It's really easy to get the good characters. Angel Power should always be as high as possible for good health, lower for less desirable characters. They get angel power from eating sweets (you can really pump in the chocolate without hurting it!) or from praise after doing good deeds. They don't beep when doing good deeds until adulthood, so you need to keep an eye out. Right after praying for you, they always poop. I don't know why. You can get the best characters without ever having to praise them, too. Playing the game is easy, and if you jump over all 5 stars, you get two hearts filled. They also evolve faster, once every day. They are lower maintenance than the P1/2. Just a warning, if you get Futagotenshi, they don't seem to want to ever die. I got to day 24 and the hearts emptied out completely every 10 minutes but it wouldn't die... took 24 hours of neglect to happen.
