>>6630229Personally it's...
1: Size. I don't want or need a 2 fuckin' foot tall Omega Supreme, or Devastator, or whatever. I want some playable. Something I can mess around with at my desk. Shit like that is a glorified statue.
2: Space. I live in an apartment, so space is always a concern.
3: Cost. I can afford 3P stuff by saving up, but it's always cheaper to buy something smaller than some gigantic fuck off near statue of a figure. I do own a mix of MP stuff and other stuff though.
4: Playability. It's just harder to play with something the bigger it is. You need way more space, especially when you add more figures into the mix for a nice little battle scene or picture taking. The bigger it is, the less balanced it usually is, and the more careful you have to be with it. It's size is it's biggest downfall, because the weight and stability in more interesting poses can drag a figure down.
tl;dr I play around with my figures, and find it easier to screw around with smaller ones.