The DLCs for Isolation mostly focus on scavenging and survival. Crew Expendable, on the other hand, is an interesting take on the game since it tells the story of the Nostromo crew after Brett's death. Remember what the crew's idea was? That is what you have to follow: lure the alien to the airlock.
While in the movie Dallas decided to accomplish this task, here you can pick Ripley and Parker, too. At the table there is a discussion (you can consider this the intro) and Lambert and Ash, too, are present. The first section is about you picking up equipment including the famous flamethrower. Then you start the 2nd section with the alien roaming around and you trying to activate terminals.
Naturally, we have the famous ventilation system section, too, where Dallas met his demise. Now you have the chance the change history (and script)! The last section is very annoying as it is difficult to lure the alien into the airlock. A lot of people say this is a bug - I think it is just a hit-and-miss part of this DLC. Once you're done, you can enjoy the outro with an all too familiar face.
Now, Crew Expendable is short but fantastic! You can walk in the Nostromo which means entering the sick bay where Kane died (the lifeless body of the facehugger can be found to the right).And, of course, it wouldn't be a proper Alien game without a dunking bird you immediately spot on a table. This is something the original actors came back to so you can hear them dubbing their lines once more but 35 years later. Great!
Apart from meeting the crew of the original movie, this is a pretty short DLC. The replayability simply means replaying it with the other 2 members to make sure you have done 3 walkthroughs. Personally, I prefer these story-oriented DLCs.