I'm very late to this, but I guess I'll do this too. My favorite and least favorite sets (minus Morfonica and RAS because they don't have enough sets yet).

PoPiPa

How to Spend a Special Day - This was a hard decision between this and the Before the Start of a New Season set, but I picked this one because light blue and pink are my favorite colors (I say that even though Aya is my least favorite character).

HAPPY Poppin' Xmas - This set is just way too generic for a Christmas set. That's basically it.

Afterglow

Cycling Seasons, Fresh Skies - I just love the shading and lighting so much in this set. It just looks so nice.

Sennetsu Sora wo Ko ga shite - I don't really dislike any of Afterglow's sets, but I chose this one because Ran's card puts me off.

PasuPare

Straight Toward My Dreams - Same reason as my favorite PoPiPa set. I just love light blue and pink. Also, the cards just look really nice.

Pastel*Palettes! Deserted Island Idols - These cards are just kinda boring to me. Their hairstyles are just their casual hairstyles and the costumes are just boring.

Roselia

Neo Fantasy Online -Ancient Dragon Bride- - Everything about this set just looks so nice. The black wedding dress just looks so cool.

Don't Leave Me, Lisa!!!! - Once again, I don't dislike any of Roselia's sets, but I chose this one because the colors and costumes are just kinda boring.

HaroHapi

The Haiku Set (I'm not typing out that entire title) - This is basically tied with the Hello, Happy World's Smiley Summer Vacation set, so this applies to both of those. Both sets just have such amazing lighting. Like even the 3 stars in both of those sets look like they could be 4 stars.

Little Smiley Steps! - Once again, I love all of HHW's sets. I just chose this one because the costumes are the most boring.

Mixed

A Dreamy Promenade - This was so hard to choose, but I chose this because wow the cards look so incredibly amazing. The shading, the costumes, everything is just incredible.

Searching for Stars - You're probably wondering why I chose this as my least favorite, since I love space. It's not that I don't like the cards, it's just that I'm mad at Craft Egg for not including Kokoro as one of the cards, even though she's one of the featured members.