The police vehicle is the first one I built. It's got a very attractive and athletic design; it looks fast and aggressive both. I was particularly impressed with the thrusters. I remember back in the very early days of LEGO Space when all you needed was an L-girder to change your stud direction and a rocket exhaust cone, and that was sufficient to be a thruster for LEGO spaceships. These thrusters now are much beefier; much more complex and attractive designs. In fact, they're very complex and attractive designs; much more complex than I'd ever seen an official LEGO design do.
I also really like the prison pod. This is now the third prison pod design (since it's the third Space Police line-up) and I like this one the best. It's made of two half-cylindrical blue trans elements, and has a fun little "push tab" that causes it to pop open, and attaches snugly to the rear of the vehicle between the two thrusters and wings. In fact, the police ship looks a little funny without it attached, although that's not unusual for Space Police vehicles of any line and their prison pods.
There are, however, two nitpicky quibbles I'd make about the police vehicle. First; the cockpit doesn't open. You have to just pull the cockpit piece off to get the policeman in and out. Would adding a hinge element have been that difficult? That was a bit of a surprising decision. The second one is that once completed, the vehicle is surprisingly flat. There's very little to it from a profile angle. It's very sturdy though; especially compared to the rickety feeling Gold Heist police cruiser.
As much as I liked the police cruiser, the criminal flier was even funner, though. It's got this combination hot rod and pirate theme going, with skull motifs, a big intake valve, racing stripes, and scattered bullet holes along the fuselage. It's got a small "pick-up" like bed in the back, with a box for stolen gold, and it shoots padded missiles from the front end. The vaguely "box-like X" shape to the vehicle makes it look sleek and predatory, as does the toothy rack along the top. It's also very sturdy, but it's also a bit flat in profile, and it also has a non-opening cockpit, so you have to take it apart a tiny bit to get the minifigure in and out.
The minifigures are also quite fun. The policeman is just another space policemen, nothing too extraordinary (although I do have to say that I really like the dark gray suits that they wear.) He's got airtanks this time, which is perhaps a little odd, since he doesn't have a fully enclosed helmet. The aliens are really cool, though... not as unusual as the four-armed alien from Gold Heist, but very evocative nonetheless. Their bodies are black, and in fact have a black leather "space biker jacket" look to them. They have pure white faces, three eyes, and a helmet/mask that makes them look like little Cthulhus.
I'm still excited about Space Police 3, and would like to pick up a few more sets, including the medium sized beefy ground vehicle 5979 Max Security Transport, and the large spaceship 5974 Galactic Enforcer. There's also a limited edition 5980 Squidman's Pitstop that serves as an alien base of sorts with a few nifty little vehicles, and 5972 Space Truck Getaway has been growing on me as well. If I get those, I might as well round out the collection, since the only sets left are the very small (and therefore cheap) 5969 Squidman Escape, with a single mini-flier, and 5970 Freeze Ray Frenzy with two very small fliers.