But specifically with respect to software engineering, it's really hard to do solid, repeatable experiments. It's not like physics, it's like sociology or psychology - which also have trouble doing precise, repeatable science.

Why is it like sociology or psychology? Because it's about people, not about things. Software engineering is not just about languages and programming techniques; it's about how people interact with those languages and techniques. The people have far more variability than the languages and techniques do. Cutting through that to be able to accurately say something about any language or technique is... really hard.