on the 1.27 and 1.21 issue.
Although both patches have interchangeable save files there is one great difference between them that heavily affects gameplay.
When you mobilise in 1.21 you can finish non military builds in your cities that alrdy started but you don' t get shield bonus military units get. Apparently there is an exploit that allows some kind of infite shield production in one turn so they changed this in 1.27.
When you mobilise in 1.27 you can finish non military builds in your cities that already started AND you get the extra shield bonus on them too. Just imagine what happens when you start a wonder, say ToE, and mobilise in 1.27. It builds like in a GA.
So you all better use one of the two patches when nationalism is available to keep the playing field level.