Firebug has better usability in the places where it counts. The result is that using Firebug is, in general, faster than using Web Inspector. Let's take editing

Firebug has better usability in the places where it counts. The result is that using Firebug is, in general, faster than using Web Inspector. Let's take editing, for example: * WI requires double-clicking, whereas FB allows single-clicking. If you think this is trivial, then try this out: Spend a day on the web double-clicking textboxes, links, and other elements that normally require single clicks. It will annoy the hell out of you, especially if you use a trackpad instead of a mouse. * On a related note, FB shows you a text-editing cursor when you hover over an editable field. WI, on the other hand, shows you the same cursor no matter what you're hovering over. It fails to provide context clues as to what can be edited. * When editing a field, WI doesn't update the page with your changes until you press enter. Firebug, however, updates the page in real-time, so you can see your changes before submitting them. This is huge. * EDIT: After spending the last hour working with Web Inspector, I was reminded of something else: For no apparent reason, WI will sometimes reject my edits. I will edit a style, press enter, and it simply reverts to the previous value. Ugh. I don't know if this is a bug or not, but I remember running into it almost a year ago (admittedly much more often than I do now, though it shouldn't be happening at all). Using Firebug is just faster by comparison. If you're a light user then it might not matter to you. If you do heavy DOM manipulation and design work on a regular basis, however, then speed is everything.