I don't understand why security-minded people seem to use Chrome more than Chromium. Does anyone understand this?
I assume you really mean "people who don't like sharing personal data". They're different things.
http://en.wikipedia.org/wiki/Google_Chrome#Usage_tracking
Chromium doesn't have an auto-update mechanism and it can be hard to find a version that corresponds to the current stable release.
Chromium also doesn't do releases, just lots of bleeding edge snapshots, and one or two of those have been badly broken.