In Shakespearean terms, a fool is usually a commoner or a clever peasant that uses their skill and wit to out-do those of a higher social status, in that sense, they are historically accurate to the real fools of their time period, but Shakespeare usually portrays his fools as caricatures of their real-life counterparts for dramatic effect, for example; by giving the fool the ability to use magic, Shakespeare created extensive opportunities for distinct and memorable situations to unfold and entertain his audience. Puck and Bottom are both very dramatically effective fools in A Midsummer Night's Dream, and we could give a strong argument for either character being the most effective. However, I feel that Puck is more dramatically effective than Bottom.
Puck is a licensed fool, as it is his job to make Oberon laugh and he is given permission to mock his world. Licensed fools are usually sad characters themselves, often outsiders. We can see this as Puck is an excluded and disliked character in Act 2 Scene 1 when one of Titania's fairies tells Puck "you are that shrewd and knavish sprite". This gives us the impression that it is common knowledge among the fairies that Puck is cold and dishonest as he often plays unkind tricks – an example of this is shown in Puck's self-confessing speech in Act 2 Scene 1 "Sometime for three foot stool mistaketh me; Then I slip from her bum, down topples she", where Puck talks about tricking a woman and causing her to fall over. Therefore we can assume – while using the quote "I jest to Oberon, and make him smile" – that Oberon is Puck's only ally. The previous quote also supports the conclusion that Puck is a licensed fool as he does not say that he jests to anybody other than Oberon.
Bottom, however, is a natural fool, he does not intend to make anybody laugh and takes himself very seriously. Bottom brings the audience humour with malapropisms and irony.