Keep in mind this is just my opinion, and only on these two sets. Feel free to have your own opinion.
I never got into mixels, never owned one. Until now.
When I first got it I was like "Gee, this seems familiar", except I didn't say "gee" because who says that.
The main build of the aqua pod is a shark. It's a pretty simple idea, but is executed very well. I like how it uses sloped tiles.
Nurp-naut is a space alien... thing. It is really creative, and I do like the helmet. One thing I don't like too much is the asymmetrical teeth, though I get that it's in the style of mixels.
The shark has plenty of joints, some for the jaw, for the tail, and even for the fins, which is a nice touch. It uses blue on the top and light blue on the bottom, making it feel very whole. I don't like the use of transparent cheese wedges though, they look out of place.
Nurp has some... interesting color choices. I like lime and white, very nice space colors, but gold? Why would you dooooo such a thing? On top of that, he has trans orange boosters, but trans red ear lights. (Okay maybe that's not as bad). What I do like are how the peet are connected, It uses an axle stub (the ones for rubber bands) as a sort of mini ball joint.
Okay, the running's been pretty even so far, maybe slightly weighed towards the x-pod. Here's what blows those standings out of the water.
The aqua pod makes three different sets. A shark, a hammerhead shark, and a walrus that can launch pieces like a catapult. Oh, that and the pod looks great.
The nurpster has an alright function... Man-E-Faces here spins his head around to reveal a different set of eyes.
So all in all, I think you know who wins. Aqua pod! Why? Because this review is completely biased.