In our opinion the astragal stile provides the cleanest finished look, as any slight imperfection in the window or wood is impossible to detect. The astragal stile accomplishes this by doing the best job of all the options of hiding any light gap. Your eye will likely notice a light gap that is uneven - even if it is very slight and within industry manufacturing standards. Because of this, unless you have a very specific reason, you should seek a shutter with an astragal stile where the shutters meet in the middle.
Keep in mind, this astragal is really only needed where opposite side panels meet. You do not need an astragal where same side hinged panels meet. See diagrams below.