The way I read the update blurb, once you install it, an updated chart card will also be able to update the MFDs.From what I was explained, you need to download everything from AC on your phone. You can still use express to DL to a card, but and according to tech support the additional downloads will not effect what's on the card.
That said, I have two 32gb cards, one has the express 18gb chart download on it and the other is for AC and re-downloaded over 6gb of data. Took all afternoon Saturday to get this going.
After all of the downloading and what not, the charts did have all of the expected features that the express download alone did not have. Sat photo's, sonar imagery etc.