We've installed hundreds of 1000.4's and 1000.2's and the 1000.2's generally give a little bit better signal, at least here in the east they do. And like was said before the 1000.2's are easier to align.
I just gave the 1000.2 dish set away a few days back to the installer for free and I told him that the 1000.2 does not peak at good signals. I have the AI Turbo S2 and no matter what I tried I couldn't get the numbers to go to the 20's. With the 1000.4, I expected a slight increase and it was easy to align as well. My main focus was 61.5 and 72.7. 77 was not what I even attempted to hit and that too came in just fine.
In my opinion, if you are still targetting 61.5 and 72.7, the 1000.4 should get higher numbers as the dish is larger. Offcourse it was designed for 77 as well. I hope dish moves the internationals to 77 from 118 so we could have a single dish solution but that is a separate topic all together.
61.5 now has open spots for the California area. Dish should officially allow the EA arch to be installed in the West coast for people with LOS issues. 61.5 was the main dish in the earlier days for international programming along with 148.