Shaikh ‘Abdul-‘Azeez bin Baaz (rahimahullaah) said:
It is better in the Dhuhr prayer that it (the recitation) be done so from the mid-length Mufassal soorahs such a soorah Al-Ghaashiyah and Al-Layl and Abasa and At-Takweer and Al-Infitaar – and the like of that.
In the ‘Asr prayer it should be the like of that – however it should be a little lighter than that of the Dhuhr prayer.
In the Maghrib prayer it should be the like of that or shorter than them, if one sometimes recites with that which is lengthier; then that is better, because the Prophet (Sallallaahu ‘alaihi wa sallam) recited soorah At-Tur within it. He likewise recited soorah Al-Mursalaat and on some occasions he would recite soorah Al-A’raaf and divided it between the two rak’ahs. However; in the majority of the time one should recite from the shorter of the Mufassal soorahs.
In the ‘Ishaa prayer one should recite the like of that which may have been recited in the Dhuhr and ‘Asr prayers.
This is likewise in the Fajr prayer, after Al-Faatihah; one should recite that which is longer than the previous ones – such as soorah Qaaf and Iqtarabatis Saa’ah and At-Taghaabun and As-Saff and Tabaarak and Al-Muzzammil and that which is similar to that.
(Taken from Al-Ikhtiyaaraat Al-Fiqhiyyah Fee Masaa-il Al-‘Ibaadaat wal Mu’aamalaat p.64-65)
 The ‘Mufassal’ soorahs or sometimes refered to as the: ‘Hizb Al-Mufassal’ are as Al-Haafidh Ibn Katheer mentions the soorahs which begin from soorah Qaaf – and it has been said Al-Hujuraat. Badr ud-Deen Az-Zarkashee similarly states that they are the soorahs which range from Qaaf to Soorah An-Naas. (See Tafseer Ibn Katheer vol 4 p.197 & Al-Burhaan fee ‘Uloomil Qur’aan vol 1 p.244) As-Suyutee mentions that the Mufassal soorahs consist of the lengthier ones and the mid-length ones as well as the short ones. The lengthier ones ranging from soorah Qaaf to soorah ‘Amma, the the mid-length ones which range from that to Ad-Duhaa; with the short ones that go to the end of the Qur’aan. (See Al-Itqaan vol1 p.63)