Hi,

I am trying to estimate determinants of corporate cash holdings for ~700 firms across 16 years by using

Code:
 
 xtabond2/xtdpdgmm
in STATA 14. In both these commands, we are supposed to specify the equation to which are instruments apply. Below is the concerned argument.

Code:
 
 xtdpdgmm: model(level|difference|mdev|fodev)
Code:
 
 xtabond2: equation(diff | level | both)
I would like to know how do we decide which option is appropriate? Moreover, what is the significance of the difference in options provided in both commands?

Thanks