The key difference is that is was established that having D/F attributes is what allows you to create a basic persona ... cyberjacks, commlinks, and RCC's all have them do any of the 3 can create a persona and interact with the matrix and not just access it.
I think I understand what Banshee’s saying but please correct me if I’m wrong. The cyberjack does allow for Matrix access on its own, allowing for the use of legal Matrix actions but it lacks the additional functions of a commlink, such as trid playback, music playback, a camera, and so on. It can be used by itself to create a persona and to defend a collection of other devices. This is something both a commlink and a cyberjack can do but a cyberjack does the defense better. Additionally, the commlink has one other feature that a cyberjack lacks, the ability to load programs (maybe only legal ones).
This is where the cyberdeck comes in. When paired with either device, you are now capable of performing illegal Matrix actions. The cyberdeck is also capable of added functions, most notably creating AROs for hacking or displaying data, entering VR mode (or, at least opening up hot sim), and storing and running far more programs (including illegal ones) than a commlink.
Functionality then looks something like this:
Commlink - all the normal, everyday legal uses of the Matrix as well as being a media recording and playback device, run (legal?) programs, access cold sim VR with DNI or trodes, creates a persona
Cyberjack - perceive the Matrix in AR and probably cold sim VR, perform legal Matrix actions, perform Matrix Edge actions, also functions as a datajack, creates a persona
Cyberdeck - perform illegal Matrix actions, display AROs, store and run a greater number of programs (including illegal ones), access hot and cold sim VR, perform other commlink functions such as media recording and playback, does not create a persona