If it's anything like onshape (the only browser based CAD I know of), browser based means: everyone uses the same version of the software, you don't have to wrestle your it department for installation rights, you can login and work on your designs from anywhere with any average laptop, there are no files (houseV3finalfinal), probably proper baked in version control with branching and merging... everything software developers take for granted that we poor CAD designers only can dream of.