The Meostars are great 15's, defiently alpha glass when it comes to 15X.
As far as comparing them to NL's it really just depends on the use, for me I already own some Razor 10's which are great for a 10x and small and light compared to most others. My hunting partner has NL12's and they are awesome, better ergonomics than any other bino I've used. The glass is awesome but for me the 12 is a weird power for binos, I don't really like hand-holding them, yes they are much better than the 15's to hand-hold with the large field of view but not as good as 10's. The NL is also are phenomenal on a tripod, for small canyon glassing they are the best I've used by far, for big country glassing the Meostar 15's outshined the NL.
The NL has a bigger field of view which tends to lead to finding moving animals better, the Meostar has more magnification which leads to finding bedded animals easier and is also better for seeing antlers (points) at long range. I do not like carrying the 15's on my chest but depending on the hunt I will just because they do work for a quick look at something and are awesome on my tripod. For me a lot of my hunting is done in timber and I leave my 10's in the truck often and just use my 7x range finder, I think for these reasons the 12NL just doesn't appeal to me as much. When I'm packing my 15's on my chest it's because we are moving from area to area and sitting down and glassing for long periods.
The quality of the NL12 really shines in a 12X, in 10X I don't really see the quality outperforming other good glass because honestly, most decent glass can get the job done at those distances. No matter what bino I have when I'm in big country I always have my big spotter with me, I've picked out so many deer and elk with my spotters over the years that otherwise would have gone unseen that it's always in the pack.