When I am investigating patch failures, I usually look at test logs only. I generally only look at task logs when compile fails, or a system failure occurs, and so there are no test logs. For my use case, it makes sense to display test logs tab instead of task logs by default.
I believe the Drivers team relies on task logs primarily for their test investigation, since there are no separate test logs, for example:
Given these use cases, I think it makes sense to have the default behavior be dependent on the existence of test logs.