I would look to some efficacy ratings of fungicides for control or suppression of the diseases you are concerned with.   If a generic has as good of a score as the "advertised superior" products... I would go with the generic products.  This is the approach we are taking.  Why do otherwise?

Here is a report of fungicide efficacy on soybeans.

https://www.extension.purdue.edu/extmedia/BP/BP-161-W.pdf

Here is a report of fungicide efficacy on corn. 

https://www.extension.purdue.edu/extmedia/BP/BP-160-W.pdf