Seagate 250 GB HDD Internal Hard Drive (ST250DM000)
Seagate 250 GB HDD (ST3250318AS)
Which one is better in terms of performance?
More aboutwhich better
ST250DM000 = more cache and faster connection, but I doubt you will saturate the sata 6gbps... honestly the performance difference would be almost unnoticeable... but from raw specs this one is better...
Mechanical HDD have a hard time saturating SATA 1.5 GB/s interface let alone the 6GB/s. Answer above is correct on the newer drive being faster but not noticeable only measurable (benchmark) difference.