Hi Lucy,
Personally I tend to avoid polyols. They don't cause me any of the stomach issues that others report, but they send my BG sky high - might as well eat sucrose. From that, I assume my body is pretty nifty at digesting the blasted stuff! However, erythritol has a different action than most of the other polyols. As I understand it, most of the others such as Maltitol enter the small intestine, but cannot be absorbed by some people, hence the stomach issues, while other people absorb them partially - hence the rise in BG. Erythritol on the other hand is dealt with by the kidneys and passed out in the urine without being digested at all. Most people seem to report this as the best polyol in that it has far less affect on the BG and doesn't have the stomach issues. I've never used it because I'm worried about whether it is harmful to kidneys or bladder - I have never seen any suggestion that it is but I've had bladder problems in the past and just don't want to chance it. Many people seem to report good experience with it. It is certainly a good sugar-substitute where sugar is needed for bulk as well as sweetens, because the granular version is properly granular like caster sugar whereas splenda is more like icing sugar. You can also get a powdered version of erythritol if that's the consistency you want.
Smidge