Maybe this data is incomplete and/or corrupt and causes those differences.
Try a bigger data extract, Florida from Geofabrik for example.
No there is no difference with this option for mkgmap! 
I am trying to test the RAW database and other downloads …
Martin
The light version has this option
levels = 0:24, 1:22, 2:20, 3:18
overview-levels = 4:17, 5:15, 6:14
The full version uses an extra level (23 zoom):
levels = 0:24, 1:23, 2:22, 3:20, 4:18
overview-levels = 5:17, 6:15, 7:14
This causes those rougher edges on the light map.
Hello ligfietser,
I have very much to do now and I have **no ** spare time for openstreetmap! 
Give me some time …
Martin