Both of those distributions include CDR reporting. There is not specific call accounting (costing) mentioned above. CDR reporting will indicate call durations and who called who (call volumes, etc). If call accounting is required there are other addons that can provide these.
I’m quite happy to see more people running Asterisk even if most of it is through a GUI (in this world of Windows most people only know using a GUI). I’d strongly suggest having another system to play with though so that whilst you are reading “Asterisk: The definitive guide” (downloadable as a free PDF file) they have something to have a go with.
It can also be very instructive to use the GUI and then examine the dial plan created to see how it all works as well.