Good idea, but…
The tile borders are often in different places as they are determined automatically based on node density. This kills any comparison of tilenumbers between versions. If the tile coordinates are equal between two versions then this is pure luck. So, unfortunately, there is no option to update only tiles that have changed data (which, judging by the mapping activity, would be almost every tile on every update anyway I guess…).
Please use ITO tools if you only download Garmin maps to monitor changes in your country.
