Abductor

The Abductor is the primary science UFO for the aliens. It has the highest abduction mission efficiency of any UFO and thus is the go-to for progressing through the alien tech tree. The closest comparable ship to the Abductor is the Harvester as they are both specialized UFOs with similar stats. While the Harvester excels at harvesting, the Abductor is very efficient at abducting. However, they are both capable of doing each other's job if necessary.

The Abductor should be kept away from human interceptors if possible, while it is a more advanced ship it doesn't have much health so it can still be shot down by early interceptors. However, it does back a decent punch and if you get lucky can take down an interceptor. With a crew of 7-11, the Abductor is a reasonably difficult ground threat, however ideally you won't get shot down in the first place.

Additionally, if you're looking for an extra boost to efficiency different alien races have bonuses when sent on different mission types. For example, Sectoids are better at abduction missions than other alien races, so you can potentially get more out of your UFO if you don't mind a weaker crew.