Just think about it, you and a couple of friends are watching classic South Park or something edgy. And then, some person comes who's not even a fan of it, demands changes (censorship) or outright turns off the program. Just why do people do this? Why do they ruin everyone's fun?
Seriously, they are. This is by far the most important issue, if they made their asses fatter it would improve viewership. If they made the ponies thicc prudes would complain, which would only draw in even more viewers. Twilight Sparkle, the protagonist of the series has a fat ass, and her teacher Princess Celestia, who's ass is even fatter.
The main reason is uncanny valley. When something looks human but not quite. A perfect example would be a robot trying to mimic being human, it looks unsettling. It's somewhat insulting towards the ponies, you have Twilight Sparkle there a beautiful unicorn and you can't embrace her just because she's not fully in human shape, even though she has all the qualifications to be a sapient-minded
Pinkie hands down for me ya can’t go wrong with the cute party pony
I like Octavia or Derpy to be on the big side
Fluttershy!!!
Applejack
My choices based on gender.
If male.
Thorax
Shining Armor
If female.
Coloratura
Coco Pommel
Derpy
Octavia
Vinyl Scratch
Discord would be fun
How about Fleur de lis?
Lyra Heartstrings
Zecora
Tempest Shadow
Cadence
Rarity
Twilight Velvet
Limestone and Marble Pie
Maud Pie
Ms Harshwhinny
Lotus Blossom and Aloe