The Secret History told Theodora's story from a first person point of view. That was both because the first line of the story--"My life began the night death visited our house"--jumped into my head and also because the reader really had to experience Theodora's rags to riches tale from inside her head.
Daughter of the Gods is all third person, narrated from Hatshepsut's POV, although it started off alternating between Hatshepsut, Senenmut, Aset, and Thutmosis. The other POV's were shed when it became apparent that this was Hatshepsut's story and no one else's. I'll probably never write another book from third person, but I'm such a fan girl of Hatshepsut's that I honestly couldn't presume to write as if I was inside her head. (Although if I had a time machine, she's the #1 person from history I'd go back in time to meet.)
The Conqueror's Wife has brought me back to alternating viewpoints, all told in first person. This will include my first male narrator (since Senenmut's sections in Daughter of the Gods were cut), a Persian princess, Alexander the Great's wild younger sister, and a super villain. I love them all, but jumping from writing a chapter in one voice to a totally different voice in the next has me wanting to throttle some of them. Or myself.
So why do I do this to myself? First, because I get bored writing in the same style. (Let's keep in mind how many times I have to read each of these books during the revision process. I think I read Daughter of the Gods about 37 times.) Second, because that's how each of these stories needed to be told. Hopefully my next book will use one of these formats and make my life a little easier.