LGA1155 is the newer socket of the two, and 1366 is on the way out. The replacement for LGA1366 was slated for Q3 2011, known as X68. I seem to remember glancing over an article that proclaimed Intel had pulled their roadmap to revise the plan. But don't quote me on that.
Honestly, I'd hold off for a bit. The rumor mill is rampant that AMD may be back in the game (or even ahead possibly) in their new iterations of cpu's (bulldozer) coming out in a few months (June 11th supposedly). Following with Intel releasing it's newer cpu's (Ivy Bridge) soon after.
Oh, btw. nVidia has just announced official SLI support on AMD 990FX based motherboards. So yeah, it's worth hanging back for a bit. Edited by Lucky 13 SpeedShop - 4/3/11 at 1:56am