I think Hilton does a much better job with brand consistency, especially at the HGI level. I've been to countless CY that have been "recently renovated" but do not come with refrigerators, microwaves, etc.

Also, I know some people hate the Hilton and Hampton clocks... but at least they are consistent.

I've had decent luck with both chains on redemption and upgrades. Marriott tends to upgrade to the best room on my reward stays in the US, not so much overseas.

Breakfast is a nice perk when traveling with family -- I usually book their rooms at a hotel my family frequents when traveling, they are aware of this but take good care of us (usually getting rooms blocked together -- without requesting, etc.)

What is key is that the staff makes the stay -- at any chain, anywhere. I had a beautiful room in Revere/Boston Marriott, but that staff at all aspects -- checkin, checkout, bar, and even housekeeping left much to be desired.