Basically inertia triggers are a single trigger that is reset to the second barrel by the recoil of firing off the first.
Some "higher end" shooters claim that when firing light loads there isn't enough of a jolt to set the second barrel and then they miss a shot.
I've shot more than a few thousand light loads and never had an issue with my beretta but apparently it's big business switching inertia triggers out for mechanical ones...
I would say if you're looking at this gun you probably aren't shooting at a level where you care by what mechanism your trigger resets .
Mechanical triggers are better for those who use the o/u or sxs for hunting like I do. It is not a matter of light loads not initiating the second barrel in my case. But if I spend 3 hours walking and then I flush a grouse, and then the shell in one barrel happens to be faulty and did not fire, I will watch my grouse fly away and will have to hope for another flush sometimes in the day
So I prefer mechanical triggers when it comes to hunting. One shell does not fire and I hear a TICK... I just shoot the other one...
So just to avoid these kind of situations...