leadcounsel,
I own both the LB and the HB, thinking there might be a difference and that the lighter one would be better for my wife/kids/smaller folks to shoulder. Compared to the major qualities of the rifle, LB vs HB makes little difference. What I say here applies to both.
This is a solid platform, recently re-engineered from butt to muzzle, though as Moderator Al and many others point out, the semi-auto gas drive is based upon the Browning BAR (as if being based upon one of the most long-lived, trouble-free actions in history is some sort of problem). The FNAR is an extremely smooth, forgiving, stable and accurate source of raw .30 cal firepower. FNH USA markets it as a police DMR (designated marksman rifle), which it surely can be/do. The DMR role is shorter range than true sniper role, but the FNAR is more toward a police SHTF rifle even than its DMR role. I think some LEO jurisdictions want be sure they're not out gunned by multiple shooters in a running chaos situation, and the FNAR can be a more-than-equalizer. Drywall, auto bodies, windows, windshields, light/medium body armour, etc. cover/concealment are not proof against full-power .30 cal rounds in rapid aimed fire.
It is hard to talk and write about the FNAR because it does not belong in a comfortable category. It is not a civilian version of a military rifle and, certainly, is not a hunting rifle or competition target rifle. This rifle is what it is, and what it is speaks to a dark fact of life, that civil society can break down or be severely tested. Not to say the FNAR is alone in this regard, but it is designed to be highly effective in meeting such tests. And, as a bonus, it's a hoot to shoot!