Atlanta is fascinating because a lot of areas of Atlanta, like midtown and buckhead, seem to be doing exactly the sort of smart building that is so apparently impossible in California: transforming inside-the-perimeter space into higher-density inside-the-perimeter space, while already being bustling business centers, to an extent I haven't seen as much in the parts of Dallas I've spent most time in (I'm familiar with the continued expansion of satellite cities/suburbs, and the use of all the land to spread things around sufficiently so that it hasn't become the rush-hour-all-the-time mess of LA, but less so what's going on in more central areas).
My guess is that the difference is that more of those spaces in Atlanta had become more abandoned residentially in the past since there was room to expand outwards, opening them up for redevelopment now, whereas in LA or SF much of the old-construction lower-density stuff has remained in continual high demand because people have already gone outward just about as far as currently possible (1-2hr each way commutes) so NIMBYism kicks in hard. Plus things like "environmental impact studies" concluding traffic will be worse, etc—I'm very skeptical of the idea that keeping density low so everyone has to commute from further away really helps the environment.
My guess is that the difference is that more of those spaces in Atlanta had become more abandoned residentially in the past since there was room to expand outwards, opening them up for redevelopment now, whereas in LA or SF much of the old-construction lower-density stuff has remained in continual high demand because people have already gone outward just about as far as currently possible (1-2hr each way commutes) so NIMBYism kicks in hard. Plus things like "environmental impact studies" concluding traffic will be worse, etc—I'm very skeptical of the idea that keeping density low so everyone has to commute from further away really helps the environment.