The Rambam in Hilchos Megillah (2:17) writes: “It is better to increase in gifts to the poor than in sending portions to one another.” If so, why in the pasuk is mishlo’ach manos mentioned before matonas l’evyonim?
The Apiriyon (see also Shu”t Tirosh Veyitzor 172) answers, that when giving tzedokah to the poor, it is very important that one should be extremely careful not to embarrass the recipient. When Mordechai instituted Purim as a day of giving matonas l’evyonim, he was greatly concerned lest it become known as the poor man’s day to receive handouts. Therefore, he also instituted the mitzvah of mishlo’ach manos so that an observer would be unable to distinguish between matonas l’evyonim and mishlo’ach manos. To conceal the matonas l’evyonim, the Megillah preceded it by writing about sending mishlo’ach manos.
With the aforementioned chiddush we can understand why no berachah is made over the mitzvah of mishlo’ach manos.
The Rashba (Teshuvah 18) writes that when one performs the mitzvah of tzedokah, he does not make a berachah - because possibly the person will refuse to accept. However, according to Rema (Orach Chaim 615:4), when one sends mishlo’ach manos, he fulfills the mitzvah even if the recipient refuses them.
Consequently, if a berachah would be made for mishlo’ach manos and not for matonas l’evyonim, it would be obvious which gift is which, thus defeating the entire purpose of instituting mishlo’ach manos.
