Are there any differences between sugar substitutes?

My doctor wants me to reduce the amount of sugar in my diet. I do use sugar in my coffee each morning. For this purpose, are there any health or dietary advantages or disadvantages to using any of the three major sugar substitutes: Equal, Splenda or Sweet 'n Low? Is one better (worse) than any of the others?

I would choose splenda as it is lower in salt content.

Splenda is best. Asparteme is best during pregnancy but can cause cancer in mice when used in large quantities. They're doing more research on humans. Saccharine is the worst for you and it has a nasty aftertaste. No matter what you use, doctors warn against drinking more than two at most diet drinks a day.

DO NOT use any of those. They are not good for you. The sugar you know is bad because it has been stripped and turned into something almost toxic...sugar in its natural form contains naturally occurring molasses and other minerals and is not near as bad as "regular" sugar.
Try stevia...it is an herbal sweetner. If your grocer doesn't carry it, check a healthfood store or online. It is sweeter tasting than sugar so you use a little less. It is a much better choice than the major substitute brands and does not pose cancer or other health risks.

Most of those chemicals can create problems
Look for a new one called "Stevia"
It is a natural sweetener, not Chemical, and I can't tell you more cause I don't use Sugar, Or any of the Chemicals, Nor The Stevia.
But Google "Stevia" and read about it.