@Zeyon  
Well most people in track are taller than their peers, not shorter; that’s a fact.

@Background Pony #EF45  
I am offering my head canon opinion on their body types. My opinion is based on what information I perceive from the show. What I have said is hypothetical guess work, and I admit I could be wrong about these body shapes.
 
Small people can be strong, tall people can be fast, and vice versa.

@Zeyon  
That’s stereotyping.
 
I’m 5’1, but the strongest of my friends. The fastest girl in my class is 5’9. I’m muscular for my height though.

I definitely prefer a more compact Dash and a slightly larger Applejack. I’m not sure if I prefer tiny, spritely Pinkie or larger-than-life, could-hug-you-to-death Pinkie. I do like a Rarity who has to work around what she’s as her own brutish size. This Twilight’s height works better before the wings or immediately after them. And Fluttershy’s a bit too exaggeratedly ectomorphic for me.
 
All that being said, I do like seeing diverse pony body types, and these are some good ones. They may not mesh with my personal view, but they’re nicely done.

I do not think Rainbow would be bigger than Applejack, she’s got to be compact and aerodynamic. Twilight is actually taller than every other mane 6 member after her ascension. Other than that okay, except for anorexic Fluttershy. This does take into account that Applejack could carry Pinkie Pie during Pinkie’s Smile song.

Dashie isn’t the shortest for once!! yay :D

This doesn’t perfectly match my personal preferences, and is therefore wrong.
 
(I’m kinda sad that bodytype_diversification isn’t a tag.)