Sorry u got me stumped.
can you please explain me what it is.
Whether 8MB or 16MB, if you get a 250 GB disk with single platter and Perendicular recording (7200.10 and may be even the latest 7200.11 series) it will be very fast. 16MB ones will be slightly costlier.
But I think 7200.11 series are available only in higher capacities and with more platters.