Lutheran ping!
I am currently plowing through City of God, and so have read more of Augustine than Thomas, but I do prefer Augustine.
Thomas has often been accused (and rightly so at times) of using circular logic. While I haven't read all of his stuff yet, what I have read is at times guilty of that.
LOL! You'll likely get some argument from Thomists on board. I'm not qualified myself -- in my simple, peasant fashion, I am content to avail myself of the riches both have to offer, each in its season.