I found a real loser of a hard drive...the WD400EB-11CPF0. The 1MiB random read time measured for it was 71ms (compare to 37ms for the ST3120026A). One word: ouch. The single-sector read time wasn't good either, but isn't nearly as bad in comparison...

Also, the WD400EB-11CPF0 is ball-bearing and very light. It seems okay for now, but only has 11,220 hours runtime.