Nothing to disclose, I purchased the products. Link is not an affiliate link.
I realize by now everyone and their aunt has posted pics of MAC's RiRi Woo versus Ruby Woo. I took my pics back on May 13th and forgot all about them. Since I was swatching other lipsticks, I decided to reswatch them, but they came out terrible so I used the first set.
All photos taken with no flash, outside, except the last one which is inside.
RiRi Woo is a tad more blue than Ruby Woo. Both are matte, but RiRi Woo is a retro matte and goes on slightly easier and a touch less drying than Ruby Woo. I like both shades, but both do not want to go on smoothly on me, as you can clearly see in my swatches. Given the choice between the two, I'd take RiRi Woo, for that extra hint of blueish and the nicer formula.
Here's a last photo, taken inside with no flash.
I hope you've found the pictures helpful, and thanks for looking!