The
prequel is actually much better.
Because Mary is a much better Main character than Yumeko.
Yumeko games are always stupid with always ridiculous bet (xxxx millions, death by poison, death by shotting, death by falling, hand cut, etc), you know it's impossible for her to loose or else it would be the end of this story.
And it kill all interest in this manga.
Mary on the other hand, win some in Kagegurui Twin, but she loose too several times because she's not a perfect human being or a genious, she's just cunning and know how to use her head.
She's much more interesting to see, even in the main story.