I just want what's easiest to pull when performing actions in activities, sales orders, potential email campaigns, etc. For example, if sending an email to a customer from an activity, I'd like to choose a template based on whether the customer wants the email in English or French. Since the fields used in creating activities (and other things, like sales orders) are based on Subaccounts in the Customer table, I figure it would be easier to place the English/French designation in the Customer table. I've had too many instances where it's been difficult to pull fields from the Contacts table on a screen that's based on the Customer table, and at the very least, having different record IDs for each can make things confusing. Also, I don't thinks there's any difference in the granularity between our Customer and Contact tables anyway.
But I do have a question: if I want a new field like this to the Customer table, is it best to add it to the Entity table? I would like to know what the "base" tables are to add fields. Also, I assume if I add the field to the Contacts table, it won't show up in either the Customer or Entity tables?