First a little physics for you from getconnected.aero, which domain name I did not know existed. (Must be British from the spelling.)
- Ku-band utilises approximately 12-18GHz, and
- Ka-band services uses the 26.5-40GHz segment of the electromagnetic spectrum.
What this means is that DirecTV uses a higher frequency which is more attenuated by rain.
It's not just the azimuth, but also the elevation.  My elevation here just south of DC is 45 degrees.  When I had a dish on 110/119, the elevation angle was so low my slant range was terrible with lots of potential clouds in the way.  I suppose my old address in southern CA would have an even higher elevation angle.  Having two arcs to use is just better than one.
The only person I know out here in the east who claims his Dish WA dish suffers less rain fade than his EA dish is Tampa8.  I suspect his local weather conditions overwhelm the elevation angle issue.  I don't know if he ever subbed to DirecTV, but I suspect Dish is still superior because of the frequencies used.