First off, I want to say that I am NOT telling anyone what to play or how to have fun, lol. Just weighing in from the source material.
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The Hobbit was not originally intended to be part of the Legendarium, and as such it contains more than a few points that are pretty dubious given what we know otherwise. This is one of those times. Giants are never again mentioned in the Legendarium, even in passing, even in LotR. I personally explain this discrepancy with the idea that they were EITHER trolls or completely metaphorical (a colorful description of a really powerful storm).
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I wouldn't go quite that far. We do have the sighting of a giant "up away beyond the North Moors" made by Samwise's cousin Hal. It's long been speculated that the so-called "Tree-man" was possibly an Ent (or even an Entwife), but that has never been confirmed: "But this one was as big as an elm tree, and walking--walking seven yards to a stride, if it was an inch." And it's pretty clear that the stone-giants of the Misty Mountains were not intended to be metaphorical, as Gandalf spoke of hoping to find a more-or-less friendly one to assist him later in blocking up the back door of the goblins.
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When discussing the Legendarium in general, I err on the metaphorical, but in game I would probably consider them trolls. Then again as in, the very nature of trolls changes between the Hobbit and LotR (and the wider Legendarium) so again, I personally chalk it up to Bilbo telling tall tales and the turning to stone was actually something Gandalf did, which Gandalf humored him by never correcting. Seems like a Gandalf move lol.
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Anyway, just some stuff to consider!
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Trolls turning to stone in daylight seems to be pretty well-accepted lore in Middle-earth; I find no reason to doubt it. Giants seem to be in a category all to themselves, seemingly much larger than any kind of troll that we know of. Perhaps they are elemental entities given physical form, unaligned with either light or Shadow.