Actually, I think the official answer is "None -- PCs don't have CR ratings." CR measures how hard it is for PCs to fight a given creature. Additionally, since the expected equipment is different for PCs vs NPCs, they don't fit into the CR scale the same way. (I've seen Sean K. Reynolds say that at least once.)
If it were an NPC (working from 3.0 here) I believe the official answer would be CR 1 for both level 1 and 2. Eyeballing it manually, I'd be more inclined to round up in the second case and thus assign level 1 = CR 1, level 2 = CR 2.