diff. between DDR2 and DDR3 RAM (2011 model)

hi, ive just order the new macbook and have been looking at RAM on crucial.com for choosing the right memory to buy.

i used the "Crucial Memory Advisor™ tool" to find to find "!guaranteed"-compatible memory for my macbook.
For model, i selected "macbook 2.4GHz intel core 2 duo (13" - white)" which it seems fits the description on the apple website at the moment and it reccommended this below..

"4GB kit (2GBx2), 200-pin SODIMM, DDR2 PC2-5300 memory module"- http://www.crucial.com/uk/store/mpartspecs.aspx?mtbpoid=AE706D07A5CA7304


but the apple website says
"MacBook uses one of the fastest memory technologies available today — 1066MHz Double Data Rate (DDR3),
"1066MHz DDR3 SDRAM" - http://store.apple.com/uk/configure/MC516B/A?mco=MTc4OTE2OTA


so my question is is there much difference between DDR2 and DDR3 RAM
and am i better off trying to find a site that sells DDR3 RAM instead of going with what Crucial reccommended?

Thanks in advance to anyone who could help me with this..... Cheers!

cheers for all the responses people... on the select model bit there's

macbook 2.4GHz intel core 2 duo (13" - white) MB467LL/A and there's also MB467ZP/A

please could someone tell me which will be best to purchase for the lastest model the one ending in LL/A or ZP/A

Thanks!