I was just chatting with *NazFX (https://www.deviantart.com/nazfx) about the fact we have a confirmed height for ponies now. However, the clip from the Friendship game blooper reel isn't easy to work with. So, here's my process for getting them accurately side by side.
So, as in the thumb here, they're together. Which is great. But you can't really compare heights. So, the limbs are all bent and may not be accurate. That's a problem. However, the heads never change. What I did next was overlay a normal standing reference over each until the head size matched up.
Like so. Unsurprisingly, the feet didn't line up. So let's fix that.
And, Wyola! Accurate pony to eques