If you have any interest in WWI, you will not be disappointed with either title.
Both titles come with a ton of WWI background info in such depth and thoroughness, that you will think that you are reading a book published by the Imperial War Museum.
The "icing on the cake" is the super high quality unit art that Jison created for both titles, that is now stock for both titles.
If you decide on France '14, I would suggest getting the JTS version.
http://johntillersoftware.com/WWICampaigns.html
If you have any more questions, feel free to ask.