The help page via invoking "help operator" in Stata suggests the two operators are the same. I wondered because sometimes operators do odd things. For example.
sysuse auto
replace mpg = . If mpg == 22
count if mpg > 0
* output: 74
count if mpg > 0 & mpg != .
* output: 69
count if mpg < 9999
* output: 69
What the example shows is that the ".", which represent missing, is a very large number to COUNT and not a NaN as most people would expect. Things works fine with SUM, however.