Aside from the locations being different and each one having an exclusive outdoor accessory, they're all exactly the same inside and out. They look the same, they have the same stuff, no difference, at all, aside from what you choose to build on it.

At least the properties in the other holds like Breezehome, Hjerm, Honeyside, and Proudspire Manor have a different look/arrangement to them.

Seriously? Why not allow us more variance? Maybe I want a stone house and not some breezehome clone that looks like it's 100 years old even though I just built it. Maybe I want it to look like a log cabin. Or maybe I want it to look like a freaking fortress.

And there's the fact that the family pretty much forces Lakeview Manor on you because the other two are unappealing. One is "There's monsters in the swamp." and the other is "it's too cold." Seriously? Too cold?!!! This is fraking Skyrim! Everywhere is cold!

Its just a small addon thats worth like 5$, be glad they gave you three houses.

Who doesn't like owning excesive amounts of land.
Plus it's nice to get away from that massively crowded house.

There are a few Achievements that come with building more than one home. You don't have to make all 3 of them look the same inside since you can choose from the list of available items for each room and either build them or not. The outside of each home can look different depending on which wings you build. I understand what you mean by wishing they could look each have a totally different design, but for the nominal price of the DLC, I can't complain.

I just picked the one the would give me more storage and also look good.

And that would be Lakeview Manor.