Ogre's are "Stupid", thus Trolls R smarter because they Regenerate.
Well, if we step back into the nineteenth century, a horse was called smart if it was very obediant*. Since Trolls are easier to control then they are smarter, in a hobbyhorsical** sense.
*Thank you Strunk and White's "Elements of style" for that obscure fact.
** Thank Sterne's "Tristam Shandy" for that useful word!