>design
Both high-tier. Snooty has beauty in relative simplicity, but Chryssi's comparatively busy design still works very well. I'd lean towards Chryssi on this one, mostly on account of her novelty factor and her fun little details.
>voice
Both good, but Chryssi's reverb is too choice to not hand her this one.
>overall theme/aesthetics
Hard to go wrong with an angsty goth sorceress. Classic archetype, and it works as well as always for Snooty. That said, a race of shapeshifting insectoid love vampires is a very novel and fun concept. Incredibly tough choice, but I think Snooty wins by an inch.
>inherent evilness
Chryssi, unquestionably. Depending on who you ask, Snooty is either just a would-be despot with a chip on her withers, or Luna having a psychotic episode that she can't be held entirely responsible for. Chryssi has no morality whatsoever and cannot be reasoned with. She is, as they say, a gigantic cunt.
>ability to plot, scheme, plan, etc
They're both terrible at this and I don't want to embarrass them by going into detail. Moving on.
>motive
Let's consult our scientific measurement system: the villain motive tier list. Snooty sits squarely at High Tier (villains retaliating against misdeeds done to them, and who may be seeking to change society as a whole). Chryssi canonically sits at Shit Tier (villains who are just evil or lust for power), and can only be pulled up as high as Mid Tier (villains who are only obeying their nature and doing what they must to survive) with some charitable fan readings about the nature of changelings and how much they might need love in order to survive. Sorry, bugbutt.
>overall quality of canon appearances
Snooty barely gets enough material to grade her on; she has about eleven minutes of time on screen throughout all nine seasons. Chryssi comes in quite strong in ACW then drops off sharply afterwards (not her fault, blame late season rot). I guess we can only really compare their 'focus episodes'. Chryssi wins that comparison by a fair margin.
>power level
I'm not touching this one. Call it a draw.
>fan content potential
Both of them live and die on what the fans made of them, since neither of them saw anything near their full potential in canon. Chryssi has inspired a lot of people to fill in the swiss cheese leg holes in the whole concept of the changeling race and how the 'love vampire' thing works, so she scores high, but Snooty takes it far higher. Moon angst is an entire genre of fan content all its own, and it's been going strong since day one.
So, to tally up:
>Snooty: better in 3 arbitrary categories
>Chryssi: better in 4 arbitrary categories
Sorry, moonfriend, but you've been defeated by entirely objective and completely scientific facts and logic. Not by much, though.