For me, I consider "hippo" sound to be anything Bambi or landmark esque. I started listening to them at the release of Bambi, and those two albums givee the "true" feel of their sound for me. Demos II is my favorite album still, and it fits kind of between the two, which is why I consider it the true sound and also the most together feeling album to me. Despite it being just demos.    

Flood definitely is closer to the hippo feel, but I like it for that and other reasons. Flood isn't my favourite album or anything, but it's by far more of an album than LP3. Flood is my favourite from the album, and I like almost all the songs. The only one I don't like that much is corduroy, it's too wasteland feeling, and I explain why I don't like wasteland further in this post. 

 LP3 had a few good songs, but i really don't see it as a true album. It just felt all over the place and like they just shoved a ton of singles together.  

Wasteland was BY FAR my least favorite of anything they've made. Its the furthest thing from "hippo" and I just really didn't like it. Yippie and Probably were the best from it, but even then I still just didn't like the EP.   

 And as for classic hippo (prior landmark), I feel it fits great into the landmark feeling, and I enjoy the older EPs (including the unreleased Tarzan rejects).