There's a good article on ITworld (originally published on PCWorld) that gets into detail about HDD vs. SSD vs. hybrid drives. I recommend reading the entire article, but here are some excerpts:

"By ditching the relative slothfulness of moving parts, solid-state drives deliver much better performance (than HDDs). They're the fastest storage option available. And not only can SSDs read and write data much faster than hard drives with most workloads, but they can also access the data much more quickly as well." ...

"Another huge SSD advantage is durability. Because they have no moving parts, solid-state drives aren't susceptible to damage or degraded performance from vibrations or movement." 

But:

"SSDs are much more expensive than hard drives in terms of cost per gigabyte. Good, consumer-class solid-state drives run about $0.70 to $1.00 per gigabyte, whereas hard drives cost only a few cents per gigabyte. Solid-state drives don't offer anything near the capacity of hard drives, either: The most popular SSDs have capacities of about 120GB to 256GB"...

As for hybrids: 

"Hybrid hard drives blend HDD capacity with SSD speeds by placing traditional rotating platters and a small amount of high-speed flash memory on a single drive." ...

"Some of the advantages of hybrid storage products include cost, capacity, and manageability. Because only a relatively small solid-state volume is required to achieve significant performance gains, a large investment in a high-capacity SSD isn't necessary." ...

Bottom line on hybrids:

"For users who don't want the responsibility of managing multiple volumes or who don't constantly work with new data, a hybrid drive can be a great option to improve system performance--all without having to give up any capacity or having to deal with the headaches of using separate solid-state and hard-disk drives."