Anomalous Materials for me. I love walking around and pestering the scientists, listening to the announcement system and blowing up casseroles. This is again, something that I loved to replicate in Hammer back in the day. Just making a place that seems busy and active.
Lambda Core represents a lull in the gameplay for me. We get the Gluon Gun, or in my case, we ignore the gluon gun for being dull and bad. The grunts are gone and have taken the interesting combat with them. The chapter relies too heavily on teleporting and platforming over green goo. The sense of place takes a complete nose dive, almost the exact opposite of what is established in AM.
Lambda Core gives me a real Sunday evening kind of feel. The fun part is over and you've gotta do these really awkward jobs that you've been putting off, before ultimately winding down so you can get up for Xen in the morning... urgh.