Inheriting test cases vs. mixing them in

I’ve come across an interesting blog post showing how to inherit
tests:

How does it stack against the usual mixing/shared_examples_for,
beautifully described in

http://blog.davidchelimsky.net/2010/11/07/specifying-mixins-with-shared-example-groups-in-rspec-2/

I.e., what are the cases where you’d do inheritance vs. the usual
shared_examples_for?

Cheers,
Alexy