You will get various opinions because Atkins is:
Excellent for blood type O non-secretors
Good for blood type O secretors
OK for blood type B (both)
Marginal for blood type AB (both)
Poor for blood type A (both)
The only reason blood type enters into it is that the genes for blood type and digestion/food tolerance are close to each other on the chromosones.
A major advantage to the Blood Type Diet s is for people who are being made ill by their diet. Great health improvements are seen by those people who try these diets. If you are in fine health, the effects will be much more subtle by eliminating toxic foods.
The other factor, of course, is the amount of weight you actually need to lose. Nobody should use Atkins to lose 5 lbs.