Its safe to say that almost every corp deck you see wants to have the maximum number of cards in order to reduce agenda density. Its kind of a no-brainer, reducing the chances a runner will see an agenda is always a good thing for the corp.
The downside of this is that you sacrifice some draw consistency, which is usually worth it, because 49 vs 45 cards doesnt affect your draw chance that much.
The thing is, it doesn’t affect the runners chance to access agendas that much either. Ofc, you have 2 mechanics going against you here, the chance of the runner accessing an agenda from an R&D run, and the increased chance of getting flooded due to mandatory draws.
Still, there is a card called Jackson Howard which helps you with this problem. And what I 've noticed is that thanks to Jackson the times I 've felt I am agenda flooded are fewer than the times I felt I wasn’t drawing something I needed from my deck. Could we make a case that for some type of corp decks 45 cards is better? Maybe NEH or combo scorched earth decks. The fact that you will also have a higher chance to draw that Jackson which helps with agenda flooding could make up for the increased agenda density in R&D.