Excuse me popping in, but I have to set this one straight.

I'm Adrian, author of the Book of Strongholds & Dynasties, which is certainly not the only book on the market dealing with political games in d20!
I think you're possibly thinking of a bit in the Designer's Notes section, where I said: 'I may be wrong, and I am sure I will be corrected several times over on the Net if I am, but I don’t think anyone’s ever produced a thorough and detailed system like this one for handling political matters in the good old d20 world.'
At the time of writing, Dynasties & Demagogues wasn't around yet, and I didn't know of any other political systems for d20, though I would have been (and still am) quite happy to be corrected on this. I was just excited to have done something that I didn't think had been tackled in quite that way before.
In the time it's taken for Book of Strongholds to progress from my desk to the shelves, other political supplements such as Dynasties & Demagogues have come out, so the statement's redundant anyway. I'd really hate for my little excited bounce to be turned into a claim that Book of Strongholds was the only book on the market dealing with d20 politics, when it manifestly isn't.
As far as comparisons between the Book of Strongholds & Dynasties and Dynasties and Demagogues go, I'm glad to say that everything I've seen to date suggests that it's not a matter of one over the other, but of both books being complementary.