Hello, the F.A.Q. (link in my signatures) describes it a bit.
The differences is the play store out of the box and a bit more optimization of google apps and google store.
The drawback of the international firmware is the update cycle, it’s always weeks behind the public Chinese “A”.
They are pretty close the same… the public Chinese misses some languages, but is better maintained.
I have owned this device since about 1 month and have the A firmware. I thought I would flash the I version as soon as I received it but am reluctant to go through all the steps and using the phone on a daily basis I have been quite happy with that Chinese firmware (except for a few bugs incl. notifications and the cursor when typing SMS). I suggest you give it a few weeks and play with the phone a little before switching to the I firmware. As Ultrametric suggested, you will have more frequent OTA updates if you stick to A. I also like the fact that you can apply themes which I believe are no longer available with the international version but that might not be relevant to you.