This sounds very interesting. Can give more details on "whisper to transcribe and make sense of long ramblings, turning a 20 minute voice memo from a car ride into a functional plan"? The apps that you use, and the workflow.
Here what I feel. Posterous v WP blog ( hosted on a custom domain and not *.wordpress.com)
Posterous : Pros
1. Very easy to set up.
2. Easy to put up photo albums (no need for plugins etc)
3. No need for upgrading etc. Posterous does that for you.
Cons:
1. Limited customization (themes, widgets etc)
2. Cannot put up ads