If I were to make the call I'd make it possible for you to see the statistics (through open source code or a game option) if you wanted to know them but for the rest the exact percentages are hidden. The consequences of the actions would be given in rough outlines rather than exact numbers, quite similar to how OP describes it.
Xcom: EU did the choice of what to research rather well in my opinion. You could tell that an autopsy of a particular alien would give you insights into it's abilities and make some of them for yourself to use. But the exact reward for researching something is not revealed until the research is complete.
Xcom: EU did the choice of what to research rather well in my opinion. You could tell that an autopsy of a particular alien would give you insights into it's abilities and make some of them for yourself to use. But the exact reward for researching something is not revealed until the research is complete.