I usually tend to go with something in between a more general or detailed approach. So, then an option would be to go with a more component/task based progress mail. E.g.

 - Slideshow: about halfway. High Priority. Probably finished by tomorrow. 
 - Layout news detail page: Normal priority. Postponed till next week.
 - Responsiveness: Minor issues on tablet and phone.

You can also list any questions per component/task. This way the client has a better overview and also the opportunity to re-adjust priorities.

But as dougp01 said; in the end it's up to the client on what they prefer.