I would agree with you that the variant that has the most VIABLE offspring (although I'm not sure what you mean by viable) is the one that gets to keep reproducing and repopulating.
But that doesn't mean its the variant that produces the most offspring, which is what you initially stated! Right? Because that's not it at all. There are proponents for both K-selected species and R-selected species. R-type species being crabs, most amphibians, fish, insects, etc etc. They have a ton of offspring in which only a percentage make it. R and K types have nothing to do with Darwin's underlying theory and that's why I tried to make the distinction from what you said.
I hope by viable you mean "best suited to exploit the particular niche it lives in"?