Okay, serious question. No, really, I do want to know.
You have a free choice to marry either any existing Mamono(s) as is, all benefits included, including a harem, or a single, limitless (in potential) Queen Shoggoth. You can't choose a harem including a Queen Shoggoth, however.
What do you pick?
I personally don't know. On one hand, I love many species and the unique abilities they come with. On the other hand, IT'S A FRIGGIN' QUEEN SHOGGOTH!! It's like a living, building sized holodeck that's in love with you! She can manifest herself as whatever you want! Though, of course, probably can't mimick many unique powers...