Any artificial product will have risks and side affects.

Nutrasweet can cause blindness if taken in very large quantities.

Sweet n Low was reported to have caused cancer, again if take in very large quantities.

The FDA has, of course, conducted studies on Splenda. Many of the studies were designed to identify possible toxic effects including carcinogenic, reproductive and neurological effects. No such effects were found, and FDA's approval is based on the finding that sucralose is safe for human consumption. They of course also think Nutrasweet and Sweet n Low are safe too, so take that recommendation for what it's worth.

Concerns have been raised about the effect of sucralose on the thymus, an organ that is important to the immune system. A report from NICNAS cites two studies on rats, both of which found "a significant decrease in mean thymus weight" at a certain dose. Again, that is probably when consuming much more than normal amounts.

Since Splenda is created from sugar, it is probably the best of the 3 as it is somewhat closer to being natural.