Odyssey planets certainly seem to have fewer loose rocks than the Horizons equivalents, and a greater region of persistence for them to so driving around in a 2km circle won't keep picking up new ones.
On the other hand the distribution of the Odyssey rocks seems to give more metallic ones than Horizons did - when you do find one at least it's usually worth a detour.
Partly perhaps that the recipes have a very strong bias towards manufactured in the first place: they're almost all one of
- 3 manufactured
- 2 manufactured, 1 raw
- 2 manufactured, 1 encoded
- 1 of each
Ones with more than one raw or more than one encoded are really rare, so you do get through a lot more manufactured than the other sorts, and there are also more types of them (10 rather than 7, excluding alien types) needing to be collected.