Iefan,
One important question is what minimum performance level for the NVG system the aviation authority is going to authorize for these operations.
Are there any required published standards? Or is like in the US, the FAA for many years being well behind the industry in NVDs matters.
I am only familiar with ANVIS-6 and F4949 so I cannot make any comparissons in terms of preference or performance. Like somebody wrote above, you have to consider also training and support.