DDR vs RAMBUS

I AM BUILDING A HIGH END COMPUTER FOR RENDERING
I HAVE TWO MOTHERBOARDS IN MIND. SUPERMICRO P4DC6 DUEL XEON 2.2G P4 AND 16G DDR RAM. THE OTHER BOARD IS A SUPERMICRO P4DC6+ DUEL XEON 2.2G P4 AND 4G RD RAM. WHICH MEMORY IS THE BEST FOR THE JOB? DOES DDR RAM HAVE AN INTERFERECE PROBLEM?