Sieges: Are some units better than others?

[Festin]

Thank you. This is actually interesting:

# For every non-mindless defending unit: (str^2 / 10) + (10 if flying) + 10*(guard skill)
# For every mindless defending unit: 1 + 10*(guard skill)

So, a generic human soldier has str 10. 10^2/10 + 10 = 20.
For a mindless unit like longdead 1+10=11.

Does it mean that undead chaff are not 10 times worse then normal units, but only 2 times, so 20 longdead = 10 human infantry in castle defence?