I personally prefer Oxypowder because it works well for me, and my constipation issues, but I've also taken Blessed Herbs & Colonix. Many people seem to love Colonix, but I'm not sure why. I didn't feel that it was anything great. It gave me alot of headaches and made me really constipated. However, their herbal formula looks really good.
The Blessed Herbs worked really well for me, but it was really difficult to fast for the week I was taking it. I understand that the product works better when you fast, but I still had a difficult time not eating. I also wasn't very fond of the shakes and stuff you have to mix up, but Blessed Herbs fiber shakes tasted better than Colonix... in my opinion.
However, everyone in this forum is a little biased to one product or the other. I would suggest you look at a couple of Colon Cleansing Reviews Sites. You will get a better idea of what you are getting yourself into. Good Luck!