The audience scheme has more chances to succeed. Specially if the
segments are well defined, as often happens in B2B realm, you have the
opportunity to delimit more uniform areas, where you can focus offers
and communication. Not to mention SEO techniques to leverage
segment-specific landing pages.
A task oriented navigation resembles applications, which may not be
the best structure for your content if you need to point exceptions
between segments. Of course, the SEO can be compromised as well.
Besides, if the tasks are evidently powerful, you can make them cross
a segment scheme using a wizard, which can (again, CAN) be a cool
interaction opportunity. It recalls me of Fidelity´s "myPlan"