I think Gris definitely has some valid points there.
Why do the trolls in The Hobbit seem more intelligent than the trolls in LOTR, and why do they turn to stone in the sunlight, whereas other trolls don't?
The thing about the intelligence is quite simple - when Sauron bred these creatures for war, he really wouldn't want to have a large number of two-tonne, extremely strong, heavily armoured and armed monsters having some free will and thought of their own.
To the issue of normal trolls turning to stone in sunlight - Sauron was a powerful Maiar, so I think that he could remove that curse from his walking tanks quite easily.
That's not all of the questions, though; we'll probably need Galin in on this one. :D