Wondering what your choices are in enterprise class drives, and does it vary by your application?
In a shared hosting environment, the benefit of SSD does not justify the cost. The bottleneck in site delivery is the network and the client's browser. It typically takes same order of magnitude of time to render a web page than it does to download its components.
The only purpose SSD has in a shard hosting plan is as a marketing gimmick to jack up the price by promising increased performance that does not exist.
True in a shared environment FULL SSD may prove more costly than the benefit. I also agree that you do not need full SSD to get good performance BUT SSD can be manipulated in many ways to give you great performance.
Because of the cost involved, when running a shared server not everything 'must' be SSD but the more you tend to full SSD the better.
There could be internal benefit. For example, you may be able to host more sites on a single server versus the same server having plain old drives. The additional sites can more than pay for the additional cost of SSD and thus increase revenue.
Depends on what you classify as Enterprise Class Drives.
Are Samsung 850 Pro SSD's considered Enterprise Drives?.