So, here's this taken from this. It's a study done on the recent Bontrager helmet. Seems legit, but here are the disclosure and acknowledgments sections. That being said, the research is interesting to read and pertinent to this conversation. It would seem, and this is my interpretation, that there is some empirical evidence that specific designs under specific conditions do decrease the likelihood of brain trauma.
I think MIPS has done similar studies in-house, as do other companies. I'm no science person though, so I don't know what constitutes "trust-worthy" published research vs. "paid-for BS" published research.
Some of the authors (MB, SMM) are co-inventors of CELL technology described in this manuscript, have filed patents, and have a financial interest in the company that owns this technology. These authors (MB, SMM) are founders and co-directors of the Legacy Biomechanics Laboratory. Several of the authors (EB, AR, ST, SMM, MB) are affiliated with the Legacy Health System, which was a partial funder of this research. None of the authors received any money or in-kind contribution for this work.
This research was supported by the National Institute of Neurological Disorders and Stroke of the National Institutes of Health (NIH) under Award Number SB1NS074734. Additional support was provided by the Research Foundation of the Legacy Health System."
Also, I generally do base part of my helmet-buying process on the tech it has, but the determining factor is the fit. Usually, I don't seem any harm in getting a helmet with tech because I can't seem how it would have a negative effect in a crash. But, I agree that fit is more important than tech, and that should be the final "yay" or "put's-back-on-display-rack" in helmet purchases.