Horses are the same size as Skeleton Horses and Zombie Horses, even though they should be slightly bigger. This would be an extremely easy fix by simply adding the line "scale": "1.1" to the scripts section of horse_v3.entity.json, and then fixing the rider position.

Horse Body Height: (Visual height only, hitbox is the same on both versions)

Bedrock: Around 1.31 blocks tall

Java: Around 1.44 blocks tall

Step to Reproduce:
1. Spawn a Horse
2. Spawn a Skeleton Horse or a Zombie Horse next to it
3. Look at the height of the Horse compared to the Skeleton/Zombie Horse

Expected Result:
The Horse is bigger than the other Horse variants

Observed Result:
The Horse is the same size as the other Horse variants