I would go with the dark one.
But really, it depends on what you want to be hired for and so which one YOU prefer.
The second one is very conventional. So as @NessIllustration says, it is a safe bet; but it is also putting you against a lot of competion (they must received colorful fairies all the time). Although it is conventional, you may stand out because of the spatial awareness you demonstrates (your scene feels 3D).
Each picture demonstrates very different skills, so really, I would send the one you had most fun doing.
@NessIllustration Thank you for the feedback! Great suggestions on the edits for the pumpkin piece. I've made changes to the illustration. What do you think? I'll work to edit the text in the meantime on the postcard. 
@NessIllustration Thank you for the tip of "Handwritten font". I really like the look of that better! 
Thank you everyone for all your feedback! I'll be working on getting these printed and sent out. 
@alexisartxox Ohhh I like this! The lightening does help, while it still feels dark and moody, but I'm seeing more details than the first time. I never realized the green thing was a cat until now! The new font also looks great!!
vanessastoilova.com
instagram.com/vanessa.stoilova/
Check out my Youtube channel for tips on how to start your career in illustration! www.youtube.com/c/ArtBusinesswithNess
@NessIllustration @alexisartxox I’m still getting the feeling that the text is slightly crowded on the back. Do you get that sense, or is it just me?
These are beautiful!!
https://sarahvandam.art/
Instagram: @sarahvandam.art and @artistsandbox.etsy
Both cards just look awesome! _
I like the vibe of "handwritten" fonts, but I would recommend to look for one that is easier to read than this one. I really have a hard time with it.
I imagine an office of an editor or AD like this: Lots of postcards at the wall and him/her passing by those daily, with eyes just glimpsing at them automatically each time.
The back of the card is never visible as the card is pinned to the wall.
SO - wouldn't you want the AD/editor to recognize your name immediately when his/her eyes move over the letters? Shouldn't he/she be able to read it also from far away - when sitting at the desk and thinking of whom to give this illustration job to?
Maybe he/she doesn't want to leave the desk and only looks at the wall with the postcards. If he/she can't read your name properly, your chances of being chosen are smaller compared to illustrators with a similar style and "easy to access" informations.
Just my imagination, as I said: Don't have a clue how the desicions are made in the end.
@Sarah-VanDam I do too. I think both the title and subtitle could be sized down in order to have more space and space them out better (including more margins on all sides to give it room from the artwork). The text is enormous and doesn't need to be that big to be readable 
@alexisartxox
@MimiHecher @alexisartxox Mimi makes a good point that cards are pinned and not often removed, and for that reason it's good to include at least the website address on the front too. Maybe on the bottom?
@alexisartxox They are both beautiful! I love the second one, as it is, and I only have one slight change for the first one--on the back I would move the witches hat up just a bit, the placement makes me feel like it is cut off a bit.
I know I'm late to the party but I really like the darker one, the lights from the pumpkins really stand out. So gorgeous! The cat made from vines is a fabulous touch too! Best of luck, I'm sure this image will catch the eye of an Art Director
@Sarah-VanDam I do too. I think both the title and subtitle could be sized down in order to have more space and space them out better (including more margins on all sides to give it room from the artwork). The text is enormous and doesn't need to be that big to be readable @alexisartxox
