It depends heavily what objective they need to accomplish. Sometimes they need to keep on moving. Other times they play more of the waiting game. Remember you start the game as a ping! token and aliens should have a lot more activations then the marines or predators meaning they are more flexible to set up formations for the next game turn or sometimes even do multiple ambushes on the enemy. Also the strategy cards can be a big game changer specially when played at the right time. But yea out of all the factions i think the alien faction is the hardest to master tho not impossible. A strategy that I use for example is sacrifice a stalker by running him through an air vent then reveal a whole line of precious predator/marine ping tokens so you know the exact locations then plan ahead for future ambushes or traps. Also some add-on models like the facehuggers have a more stealthy playing style.
At the moment I like playing with the aliens
