nVidia 930m. There is no "GT 930m", just 930m.
The Intel HD 520 is only considered to be equal to the nVidia 820m. That's actually pretty decent considering the HD 520 is integrated.
Currently the most powerful Intel graphics core is the Iris Pro Graphics 6200 (Broadwell CPU generation) which is considered to be equal to the nVidia 940m. But it is only found in certain quad core CPUs in laptops that generally costs $1,000 or more.
The most powerful Intel graphics core in the current Skylake generation CPUs is the Iris Graphics 550. But sadly it is currently ranked below the Iris Pro Graphics 6200 by Notebookcheck.net... at least until they run some games on it to determine it's true performance.