Just for the sake of argument, this came to mind and i looked for official sources but couldn't find one...
Let's say i cast a 20th level GMW for a +5 enhancement on a +1, Undead Bane Longsword.
How is it considered against undead?
Option 1.) Simply +5, because it's a bigger value than the +1+2 usual enhancement
Option 2.) Add the +2 from the "Bane" to the modified +5 enhancement of the weapon, resulting in a +7 enhancement weapon against undead.
In other words, what is the "normal enhancement" referred to in the "
Bane" weapon ability description? The base value? or the modified one?
EDIT: (er... math
typo?)