RAM question

is it better to have more ram or faster ram
for example
8gb of 1600
or
4gb of 2100

 

Ram is where your processor puts the things it has gotten out of the filing cabinets (drives and storage) so it can execute or process those things. With the exceptions of gaming, some CAD packages, and very high end databases; too much ram will just be wasted money.
Further, the O/S you are running will have specific limits on how much ram it can use.
Normal XP users, for example, will almost never use more than 768MB of ram and, without special switches, XP won't recognize more than two GB.
Too little ram; though, causes your O/S to have to clear space in the ram (virtual memory) in order to load the thing it thinks you need at that moment and, because the hard disk drive is 10-20 times slower than ram, the system turns into a tricycle (slow as cr*P).
Faster ram can add 5% to the system's performance; but, only if the systemboard will run the higher speed and, regardless, too much ram won't help anything.
For XP, 1GB is tons, for Vista/7, 2+GB is optimal