First, I've had both treatments. Obviously a colonic I can't self administer, whereas, as you indicated, an enema you can. Personally, I prefer to have an enema given to me, especially if I can get a colon rectal tube used and administered high into my large intestine for cleansing. I think this would be better than me trying to administer one myself. That's why I'm interested in finding a person in the NYC area who would be able to do such a procedure.
As well, I've heard and been told a colonic has a better reach. Not for the sake of arguing, but I think a colon rectal tube will be better due to its ability to be inserted far deeper than a colonic irrigation specuulum.