Many Notaries do double duty by performing notarizations for their employer and outside of their regular job. Some might be tempted to keep two sets of journals in order to keep their two Notary roles separate. That is not a good idea.
A journal is supposed to be a complete, sequential record of all your notarizations, not just the ones done at work or for a side business. You do not have a different commission for each role; you should not have different records. Maintaining two journals also multiplies the number of things you have to keep under lock and key, and doubles the chances that the information in your journal might be misused by unauthorized individuals.
In this instance, two is not better than one.