Actually Mike, W296 and H110 are the same powder. They are both made by
Primex Technologies as are almost all Ball powders. Both powders are made the same in the same batches and shipped to both Winchester and Hodgdon for packaging. The only difference is the can you buy them in. The differences you will notice in the reloading manuals comes from small differences in testing procedures, chronographing, pressure testing, barrel lengths, etc., etc.
That said, it is still a very wise procedure to reduce a load 10% when changing any component. However with the known nature of W296 and H110 to cause problems when reduced, the reduction figure is 3%. Also, I still think it is wise to stick to loads stated for each specific powder if at all possible. Not all reloading data is totally interchangable for the two powders even if they are the same due to the factors stated above.