Currently, 2.5" enterprise drives are leaving their 3.5” competitors behind. They're faster, more flexible, and now they offer comparable capacities (we're up to 1 TB now). In this piece, it's Hitachi versus Seagate battling for high-density supremacy.
Toms with some more review niceness. Thanks for another interesting article. I don't think mechanical storage is going anywhere soon. For better and worse we'll still have it around for a long, long time to come. Even when SSDs hit that magical speed/capacity/cost point to be ubiquitous for mainstream consumers, enterprises will still need HDDs as part of their storage needs. HDDs are at least a known quantity that are still getting better.
3rd paragraph: "have to be taken into considered". You also didn't mention capacity and cost/GB, where mechanical disks still reign supreme.
Also, why not benchmark a 3.5" disk, but only use the outer portion. If both that and a 2.5" have the same density and rotational velocity, then the 3.5" should win due to higher I/O speeds resulting from higher linear velocity.