When I am giving a reading from Spirit, I relay messages from Spirit to you. When I am channeling, Spirit talks directly through me. So when reading Spirit says something to me, and then I repeat back to you. In channeling you get the information directly.
In both reading and channeling, I am in a semi-trance state. However, the trance in channeling is deeper. Some channels completely leave their body as it were while the channeling takes place so they are not aware of what happens during the channeling. Most channels including myself are fully aware of what is going on at all times, which allows me some control of the channeling especially allowing me to stop the channeling at anytime.
The downside of staying present during the channeling is that there is more of me and my interpretation in the messages given thereby reducing the accuracy of the message. On the upside: besides maintaining control with a potentially troublesome spirit, being present allows me to see more what Spirit is saying so that I relay that to you. So for example, sometimes Spirit will show me images, which I can come out of trance to describe to you.
Note that most of the messages that come from any spirit are through thought transference leaving me as the channel to put into words. So there is always some interpretation going on. Also note that since I am in trance, I may not be able to remember much of a channeling session even though I was aware of what was going on at the time.
While channeling I may take on some of the charateristics of the spirit in question. Spirit can't change my voice, but it can come through higher or lower for example.
As far as which is better: reading or channeling: Reading usually works better because I can interact with you more whereas in channeling I have my eyes closed. In channeling you interact with Spirit directly. In most situations channeling is not possible because the environment needs to be controlled so there are no distractions. In channeling I also allow more control to Spirit, who may for example get very loud, which would not work in a public place. Channeling works best with a enclosed group or private reading.
To see me channel, check out my YouTube Channeling playlist.