With the Blackwater, Neil Marshall was brought in at the last minute to direct the episode and the previous director had been very conservative with his prep and plans. Marshall did a lot of prep for the episode on the fly. Fortunately, GRRM had written the original script so it was rather OTT in the first place so Marshall was just able to put back in a lot of what the producers had cut for budget, and got some much bigger results for the money. Still, with the Blackwater they lost a lot of the scale and size that Marshall could have done with more prep time.
With the battle here, Marshall was on board from Day One and was able to plan the battle with the writers and CGI guys in much greater detail and in terms of what they could put in. That makes this episode look a hell of a lot better (there's several times the number of CGI establishing shots as in BLACKWATER, and there's no way they could have done something like the panning one-shot through Castle Black in that earlier episode as there was no time).