Depends on who you talk to as per there personal preferec how ever Rambus is mucyh faster up to 10 times that of sdram(pc 133 pc100) and faster than DDR. However it is only because it operates on a 400mhz+ bus speed. Currently there are no real programs that can take advantagre of the higher bus so it is kinda half dozen one or the other. If you are looking towards the future DDR or Rambus is the only way to go. And if you are looking at Gaming in My opinion you can not go past a AMD which works at 9 opereations per clock cycle compared to the 5 for a P4. But there again it is who you talk to. I own a small computer co in Victoria Australia and recieved a few memos recently from Intel pushing the DDR to bring down the price of there systems... but i ramble. Really it is a personal pref and if money is really no object i would go with the Rambus.
One more thing try looking into this combo it is kick *** for gaming as i currently have 3 machines running them
Amd k7 XP 1900C
Epox 8KHA+ Motherboard DDR (plus epox CPU cycle can run up to 200mhz and more to come in the following weeks with a simple bios flash)
512 DDR 2100
64MB Geforce2 GTS DDR (which actually out preforms several categories compared to the Geforce 3, or so mad onion tells me..lol)
Compared to a P4 it may save you a few bucks and is really quit a kick *** Gaming machine But then again I prefer AMD i prefer speed not so call stability...lol... P4's kick *** to however
Have fun