These are both noted in the MSL as administrations under "Yun-nan", with Da Gu-la (Lit: Greater Gu-la) being obviously the stronger. In the seventh chapter on "Geography" in the Ming Shi, it is noted that Da Gu-la was Pegu. This identification has been followed by most modern scholars, including Chen, Xie and Lu (1986; 139). Chen Ru-xing (1992) also considers Da Gu-la to have been Pegu, as evidenced by the "Takkola" of the early European maps, but believes that Xiao Gu-la was the "Gaur" of Assam. I would suggest that the identification of Da Gu-la with Pegu is entirely erroneous and that Da Gu-la and Xiao Gu-la were the polities of the Ahom, located in the Brahmaputra Valley in today's Assam.
The fact that, in 1408, Da Gu-la attacked Meng-lun (in today's Northern Burma), Di-ban (Tipam) and Ba-jia-ta (Bakata) and carried off their people (Tai-zong shi-lu, juan 82.1a-b), suggests that this was an Ahom polity rather than any polity centered on Pegu. The text quoted under Ba-bai/Da-dian above, which noted that Da Gu-la lay to the west of Lanna, also supports this proposition. It may even be the case that Da Gu-la and Xiao Gu-la were the pre-Ahom polities, as the name of the Da Gu-la ruler recorded in the MSL -- Po-di-na-lang-- suggests "....narayan", a very common epithet among the Koch and Kachari rulers.
Da Gu-la and Xiao Gu-la (Lesser Gu-la) seem to have derived their names from the banks of the Brahmaputra they occupied. In a study of pre-Ahom Assam, Lahiri (1991; 133, 138, 144, 147) notes how from the 9th century until at least the 11th century, the northern administrative division was termed "Uttara-kula" (northern bank), while the southern administrative division was named "Dakshina-kula" (southern bank). I feel that it is in these terms that we should seek the origin of the Chinese names Da Gu-la and Xiao Gu-la. Regardless of whether these were Ahom or pre-Ahom polities, the obvious links between the Ahom and the Möng Mao polity of Lu-chuan need to be studied far more deeply. The marked similarity of the list of Ahom rulers with those of the Tai Mao cannot be coincidental. For some relevant literature see Lahiri (1991), Phukan (1990) and Tanabe (1991; 28-34). For information on further Chinese sources relating to these polities, see Chen, Xie and Lu (1986; 139-40), Fang Guo-yu (1987; 1010-14) and Gong Yin (1985; 207 and 1992; 627).