Well it used to but Mobil's PDS now sucks. They used to publish HTHS which could be a deciding factor on which oil would be better in the OP's situation. Went to Mobil's site today and much of what they used to claim is no longer listed. So I have to say you are correct. When Mobil did publish HTHS 10w-30 was much higher than 5w-30.
I know someone who just killed their Toyota Corolla engine within two weeks of adding Lucas "Honey" oil treatment I advised him NOT to mess with. Engine was kia in less than 300 mi. Oh well. Sure it was worn some but was still running. Now its got grass growing around the tires sitting..