I didn't buy the GOG versions, but I do have the DotEmu published ones from Humble Bundle's "Humble NEOGEO 25th Anniversary Bundle" from December 2015. That set had 23 DRM free NeoGeo games all of which, once installed, have a ZIP file with the roms in it under the install folder which pretty much exactly match the MAME sets (ZIP file name, CRCs, etc). The emulator that DotEmu used is garbage.
Based on the comments on the SNK GOG community board they are largely the same sets with some possible updates. Someone (not me) already posted how to use the ROMS in another emu.
To get a legal edition of the 15 games GOG has so far it's certainly reasonable option.