I would definitely go for 2 DP's since led fixtures are extremely demanding for they use HTP channels and as far as I know when dealing with loads of HTP channels it's better not overloading the DP's whatsoever: If you search the forum here I'm pretty sure you can find an awuful lot of threads ragarding how to handle large amount of HTP channels and how to distribute the dp's load Marco:hogsign:
I recently had a show with 2 DP's and 8 DMX-lines. The least used line had 469 channels. Everything worked perfectly, no hick-ups, no delays, nothing. I know I couldn't do this like 8 months ago, so software is improving. It was mostly moving lights though, not so many LED's and dimmer-channels.