256mb DDR400 vs 512mb DDR333

i've been reading threads covering DDR and RUMBUS. im begginning to understand abit about the difference. but there's something i dont unerstand AT ALL!!! so please help.

would there be difference in performance between
[DDR400] 256mb PC3200 memory vs. [DDR333] 512 mb PC2700 ??? im having trouble here.
im not too bright so i would think that maybe the 512mb would be better but then its DDR333 vs the 400. i dont know. *help*

specs would be:

P4 2.26 @533mhz fsb
[DDR 400, 533mhz FSB] AOPEN mainboard SIS chipset
80 gig ata-133

thanks guys.

ddr 400 is going to be faster but if you want my honest opinion, its worth it to loose a little of the speed if it means haveing 2x as much ram
remember your computer is mainly limited by ram, with cpus as fast as they are these days, a low amount of ram makes a cpu not as useful, if you have more ram, your cpu will be able to do much more things much faster

plus its like the ed of overclockers.com said, what good is ram that runs 400mhz if the FSB is only 200mhz?
in his words its like trying to put 8 cars on a 4 lane highway
whearas with your ram being equal to your cpU FSB it makes the data flow faster and with more memory you can reach the full capacity of your cpu
i have a choice of using 512mb ddr 333 or 768 at ddr 282 (same as my FSB) and i have found thru testing that more ram at the same FSB speed does more good than less ram that runs faster than the FSB of the cpu

given your p4 tho, it would be best to get the fastest ram you can, as it needs the bandwith, so get fast ram and plenty of it =)