Which is more impressive?

I would probably say the second scenario. In baseball, pitchers have a heavy advantage over hitters. It is easier for them to "take control" of the game, especially when facing a weak offensive team. As a hitter, it can be difficult to make an impact on the outcome of a game. Going 4-4 and having 2HR all in the same game is very impressive, not taking anything away from how difficult pitching can be. From my own experience, pitching consistently well is easier than hitting consistently well.