Samsung eco-greens are “fast” 5400 RPM. I have read many review where people say this. Find it more responsive than their 7200RPM
Of course all things being equal 7200rpm drives are faster but...
I'm sure their Marketing Department has come up with some inventive way to demonstrate that "less is more", such as carefully selected test results that work on having data in a local cache, etc. Or they've got some very intelligent controller that optimizes for certain conditions common to (say) Microsoft Office tasks. You are correct to say that "all things being equal 7200rpm drives are faster"... marketers don't bother with such technical details. They're only interested in headlines.
But as we all know, rotational speed and seek times are based on physics, not marketing. :)
And while you -can- find dumb 7200 RPM drives that have slower response than intelligent 5400 RPM drives, that's not "all things equal".
And as an aside, you'd be surprised how many people think that because their SATA drive has a 3Gbps serial interface, that they'll get 3Gbps of data from the drive. 20% of that is more realistic. Yet the marketers will quote the interface speed as if it means anything... *sigh*