RAM for classic iBook

[David Crump]

I have a 466MHz Clamshell iBook SE with 256 MB in my RAM slot and am 
toying with the idea of maxing out the RAM.  I got the following 
information listed on MemoryX's website:

512MB PowerBook G4/KingMax PC100/PC133 SODIMM (p/n APL144Y512L)
$94.60

512MB Apple PC100 PowerBook iBook SODIMM (p/n APL144X512G4)
$94.60

512MB Apple/Samsung OSX/OS9 Low Power PC133 PowerBook SODIMM (p/n 
M8631G/A)
Apple Store Price: $200.00
MemoryX Price: $168.80

My questions:
a) why are there both PC100 and PC133 RAM listed?  Can both be used in 
my iBook?
b) Is the "Low Power" RAM really worth that much more?  Does it help 
battery life that much?  Any experiences with it?
Thanks in advance.

David Crump

P.S.  I bought my 256 MB chip from 1-800-4MEMORY, and have no 
complaints, except that their website doesn't seem to think that my 
iBook can take 512MB.  Too bad, because their prices are cheaper on the 
256MB sticks.