are all fibers created equal?

[MissToodles]

fiber seems to be everywhere. in fact, I noticed the pudding I was eating had 4 grams of it in the form of inulin. Since we're supposed to eat insoluble fiber to lower cholesterol among other things, are they created equal? Are naturally occurring sources of it i.e. beans/oatmeal better for you than a fiber one bar? I'm a quasi vegetarian so I do get a lot of fiber from veggies and beans, but can't find the answer, just wanted to know out of curiosity. One thing I do notice is when I eat products with added fiber is that they cause much more gastroinstential issues then the natural stuff. maybe it isn't a good thing? or there hasn't been enough studies done yet?