It's those minor but intuitive things that we get used to when using firebug. For example: 1) The inspect tool is at the bottom on chrome dev tools. It would have been much more intuitive to keep it at the top of the bar.

2) You don't see a change of cursor when hovering over editable properties. People who never used firebug might have gotten used to this but for me it feels clunky.

3) No single click edit. On firebug you can start editing a property with a single click. Not so on chrome. This is even worse when editing styles. When single clicking a style you don't even see a visual indication that something happened... again feels clunky..

4)Too many tabs that are not bunched according to how often they are used.. I don't think people use Resources, Timeline, Profiles, Audits as often as they use the other tabs.

5) The information is presented in more readable way. When a break point is hit, chrome displays a bunch of tabs on right which are vertical (often empty - because they aren't relevant to this break point) and wasting precious vertical space..

6) Clutter, clutter and more clutter.. just too many sub windows cramped into one another affecting readability...

I know that most of these reasons are subjective and vary across developers but wanted make a list of my own reasons as I found my self trying to use chrome dev tools and always jumping back to firebug.