Well, I'd recommend looking at some benchmarks, such as this, for example:
Of course, real world usage is the ultimate test, as the SSD caching might not always come into play in synthetic tests (or might come into play more than usual) and the caching performance increase might change as the drive fills up with data.
I have a Seagate Momentus XT (500GB 7200rpm hybrid drive with 4GB of SLC flash). Its a native hybrid drive. Its a bit different from these options where you pick the SSD and HDD yourself (since obviously nobody is going to buy this and use only a 4GB SSD), but it works on similar principles.
- You get the benefit of SSD's low seek times for most data, and the high capacity of a conventional drive
- MUCH Simpler and easier than using the drives seperately and deciding what to put on them
- (hopefully) less wear and tear on the SSD, so it gains a longer working life - Although this depends on how the caching works
- Not everything will gain a performance boost, and you won't get full SSD speed all of the time
- Synthetic Benchmarks don't necessarily show the true performance benefit, it can be much more (or less) in real world usage
- The caching algorithm won't cache data until after you've needed it a few times, so it won't be fast from day 1, it'll get faster over time
- The controller is more complex, so it might add to latency if the controller isn't very good
- Depending on the interface they use, it might not be possible to use these as a boot drive, so make sure to double check if you want to use it as a boot drive
I see the hybrid model as the easy "fire and forget" option, when compared to having the two drives seperate and deciding what to put on each drive. The thing to remember about hybrids is that they usually feel more like a fast hard drive, not a true SSD.
Consider that you might gain more benefit by installing your OS and performance-critical apps onto an SSD, and then putting less important data on a regular HDD. And don't expect true SSD speed - My hybrid drive does make my laptop a lot more responsive, especially during bootup, but its still way behind an SSD. Of course, what you're looking at may be different, it depends on the ratio of SSD capacity to HDD capacity. I have 4GB to 500GB, with a product like this you'd probably be putting in an SSD that is much larger than that.