When you divide a division that is in rest or reserve, /A always improves it's exp, mor, fat and dis faster than /B or /C. This is irrespective of the leaders assigned although they do obviously have some influence. Been like this since WitP day but you can get round this little quirk by recombining regularly.
The better the division leader is the better the subordinate leaders tend to be when you divide a division. At least this appears to be the case when I do it.
