Actually it should not make any difference, and I wonder how in your case the timestamps can be different at all.
But the Page API does not provide any way to read that (I see a "getLastModified()" method, but no "getCreated()" method, which is a bit inconsistent), therefor I would stick with the method you already have. As said, I cannot explain the inconsistency, but this property is not protected, and thus can be changed at will.