How much benefit (if any) you see depends on the workload and I/O profile.
You need to do an analysis and determine what makes sense.
If the application spends a lot of time reading its executables and libraries you want to put the application itself on the SSDs.
If the application spends a lot of time reading data files you want to put the data files on SSDs.
If the application spends a lot of time doing read/write I/O to its data files you want to determine of the SSD's write speed will be an issue (if the SSD write speed is as good or better than rotating disk you can see a performance benefit, but if you spend a lot of time writing data and the SSDs take longer to do that you may see a performance decrease)
Also note that if you're not saturating your disk's I/O bandwidth (hitting the disk's limits) SSDs may not give you a meaningful performance increase at all: You can read data faster than spinning disks can, but if you don't actually need that speed the performance improvement will be negligible.
Similarly if your disks are saturating your controller's bus SSDs won't help (the SSDs will also saturate the controller's bus, and you'll see identical performance) -- SSD or spinny disk your limit is still the controller.