From the sounds of it you won't be able to choose between the two anyway.

You can get:

DDR 233, 266, 333 and 400Mhz or
DDR2 400, 533, 667 or 800Mhz

DDR and DDR2 are not compatible with each other so unless you have one of the rare motherboards that support both DDR and DD2.

DDR2-533 is always going to be faster than DDR-233/266.

Are you planning on getting more RAM for your laptop? If so you should check what RAM it supports before buying