Pick any basic mil spec BCG from any reputable manufacturer and you'll be solid. I try not to get wrapped up in the lightweight gimmicks, and all the "increased lubricity" time wasters like NiB or TiN coatings.
In my experience, not one does anything better than the other, so it comes down to a simple question.
Do you want to spend some money and get results, or spend more money and get the same results?