Iowa State University Extension does a large scale fungicide testing trial for both corn and soybeans annually to compare new and existing fungicide technologies. 

There are differences in the modes of action between fungicides which can impact effectiveness based on diseases they control including disease type, timing of disease onset, past fungicide use that could lead to disease resistance issues, and overall timing and type of application. There are also differences on the type of plant health benefits these products can influence. 

Bottom line is that there is no singular right answer on what fungicide may be right for your field since there are a lot of factors. The best bets are to understand what is going on in your field and use any past history and your prior field management as a guide.