Pro Emotions mechanic gives a feeling of realism
Emotions replaces the old system of traits. Using emotions to regulate how sims behave does feel more natural to a way a person would behave making for a more realistic feeling simulation. This allows the player to feel more immersed in the game.
Con Missing features that were in previous versions
The Sims 4 is missing a lot of features and options that were in previous version making the title feel unfinished or rushed. Of course it all could be a ploy to sell these features to the consumer at a later date basically making the users pay for the games content piecemeal.