I think Asmus posed the question about the paint -- so I'm guessing the sculptwork is done.
I see Frodo's nose and Sam's 'fatness' as the biggest issues with the sculpts. But again, when the sculpt is the size of my thumb I'm a lot more forgiving.
I have a suspicion you're right. Paint is good. No bueno on sculpts.
True, scale is a big factor. But I'm struggling to find resemblance in the Frodo sculpt. His cheek structure is dead on. The rest... lots of areas are subtly off, some majorly off, but it all just gives me a big impression of
off. The shape of the upper lip is good, lower lip slightly off. But the mouth isn't in the right position compared to the nose (length of philtrum is way off); the bottom part of the nose is pretty close but the bridge is weirdly creased in a way Elijah's doesn't crease in real life, the eyes are incorrectly placed by just a few smidgens and his left eyelid is slightly misshapen, the chin is disproportionate to the mouth, and the hair strands are a bit chunky and undetailed.
The philtrum and the mouth being too low on his are the main things throwing it, but the eyes aren't right either. They're all that's off, really, but the overall effect is devastating IMO.
As for Sam, the mouth and the chin are just wrong, the jawbone structure is hidden by fat that wasn't on Sean Astin's face, the eyes are ok, the nose is slightly off and the bridge of the nose is correctly creased when compared to Astin looking a bit moodier, but isn't really right for the expression on the rest of the sculpt, and the haircut is too much of a bowl cut from what that picture suggests.
Those are my thoughts on this.