The tradition with HDDs is to spread them out on multiple drives to prevent input/output drive bottlenecks. All of the article in the Adobe libraries (that I've found) are aimed at users with workstations that have multiple hard drives and various backup systems. Few articles have mentioned SSDs as apparently they have not been considered trustworthy.
I have a new ASUS i7 laptop and am very happy creating a new folder for each project and putting everything in that folder. I create the folder, put copies of the media I plan to use in it, start a new project and double check in preferences that scratch disks are all set for "same as project".
Since I use the SSD as the work drive, my HDD is for storage and less significant software installations. At 7200 RPM it is relatively fast, but not that important for they way I manage video projects.
At output I get near 1:1 render times, unless there is significant use of effects and multiple video tracks.
The laptop has a 7200 RPM HDD. I tried various suggestions for spreading out the source, temp and output files and got no noticeable improvements in performance. So, if you choose to manage projects like I do, it does not matter much what HDD you buy.
When a project is complete I move the entire folder to another drive for storage and back that up on yet another drive. If I want to work on a project, I can move the entire folder back to the SSD. I find it very convenient.
Message was edited by: whsprague to correct spelling errors!