ONE WORLD, OR BOTH

I have a question to ask my readers. Something I’d like to ask your opinion and advice on.

I have been working a series of three novels now for awhile. I keep going back and forth on how to best arrange the overall story-line and plot. The tale takes place on two different worlds. Worlds which are separate and distinct, but ultimately related. One of those worlds is our world, circa 800 AD (in the Byzantine Empire, northern Africa, and the Middle East), and the other is another world, at about the same time period (though they reckon time differently).

Without becoming overly complicated in my request my question to you is this:

As a reader would you prefer the first book to take place in only one world (our world for instance,) and the second book to primarily take place in the other world, (the third book will move back and forth between these two worlds), or would you prefer the story to move back and forth freely between both worlds in all three books?

I have been going back and forth on which idea would be better as a story arrangement and plot device. And have still reached no definitive conclusion.

So to you, as a reader, which would you find more pleasing and interesting as a story form or manner of progression – One World at a Time, or freely skipping from One World to the Other in all three books?

By the way here is a link to some of the posts I have made about this book series – The Kithariune