if your currency is shekels maybe you shouldn't be buying computer parts. i know a good market that sells really fresh figs. shekels sound like they're good for buying figs!
.... but to answer your question, if you're comparing 256mb to 256mb and 512 to 512, then just get the cheaper one. they should both perform the same.. just check out the bundles and see which one you'd like better, and if its worth the extra $$ if its more expensive..
but seriously stick to figs.
"Is virtue a thing remote? I wish to be virtuous, and lo! Virtue is at hand." -Confucius