I think people generally have their own preferences when it comes to bowel cleansing. Some people find great results on certain cleanses while others do not. I haven't tried a lot of the cleanses, so I wouldn't be able to give you an unbiased opinion. However, there have been some concerns about certain cleansers. A side-effect of a colonic could be back-wash of colon debris settling back into your body. Though I'm not sure how much of a concern this should be. Also, you might be concerned about certain cleansers that have a laxative effect on the body, in the sense that the body may become too dependent on the cleanser or possibly weaken the bowel walls. I was told the herb Senna is a red flag item because it is essentially a laxative.
You might want to look into colon cleansing forum and see what the members are suggesting.
Feel free to email if you want.