When I migrated from Hitachi 500GB to 750GB, I chose WD WD7500AAKS based on price/performance.
Look up some compro reviews, and I suspect you will see what I saw.
I haven't used the Hitachi but I like the WD quite a lot. My 320AAKS drives were quiet but this one is quieter than those - and also blew away my other drives on HD Tach. Nice article here: