The age old question! And one that many Salesforce blogs and success communities have debated for different scenarios. TaroWorks can create and update both Standard and Custom objects in Salesforce. There are two main TaroWorks considerations for choosing between a Standard and Custom object.
The first is the main TaroWorks implication for your database design, which is mobile record assignment. The only way the "Standard vs. Custom" argument could play a role in the use of the mobile record assignment feature, is that standard objects cannot have custom objects as parents in a master-detail relationship. So if you wanted to raise your mobile record assignment level above the Account object with master-detail relationships for example, there will be limits.
The second is that TaroWorks does not map to all data-types. So there may be some fields in standard objects that would require automation to facilitate population or associated processes.
Generally, TaroWorks is not the main driver as to whether to use standard or custom objects.