This is similar to other suggestions already here (red ticks to show data present; default to a particular tab).
I think Bio1 should have on it the primary contact details, so there'd be up to five (as only one per tab can be primary). This way the primary details would be visible upon opening a constituent, without the need to click tabs to see the others. Also if printing from the screen this would remove the need for two screen shots.
Perhaps also have it so they show in an editable grid, so they can be updated in the one place.
The default tab is a good idea; perhaps that can be a per-user setting (as one user could be focused on emailing constituents, another on phoning them).
Perhaps the above two features, as well as the red ticks (this could show even if there is no primary value but there are other values), could be implemented.
7.94 Update - This is along the same subject line as the above idea - in the Business tab, when I enter the Phone and Email and then go to click a check mark in the box for Primary, it does not allow me to do this, it only highlights the whole line dark blue. When I set the Business Address as Primary, the Phone and Email do not also transfer over to Bio1 as does the Business Address. It would be great if we could have the capability of setting the Phone and Email in Business as Primary and if they could both also transfer over to the Bio1 tab once the Business Address is set as Primary.