Recent A7/8 updates (particularly view_check) make it easier to optimise CSM. Also, nice outdoor shadows have been an expectation in games for a while, but SSAO is much newer and still perhaps considered a luxury.
Finally, CSM is much more scalable than SSAO (that is, you can have decent looking shadows on old systems, and then insanely realistic soft-shadows on newer systems -- I've seen how SSAO can be scalable, but the visual cost means it's often not worth it at all, IMHO).
So CSM's where my vote goes
Great shots, btw.
Jibb