Brande,
The guys here at work have tried many varieties of the auto-darkening shields and we require hard hats in the shop in addition to the welding shield. Herein lies the problem with the Speedglas vs the Jackson Executive in our shop. (haven't used the Nexgen, yet)
The Speedglas utilizes it's own version of a hard hat which requires adapters, the bands break that allows the shield to slide up and down and guys are frequently sending their equipment back for service and are unhappy with that service to boot.
The Jackson fits our company issued hardhats and we add the little ears to hook the shield onto ...all Jackson stocked, no special hardhats or adapters with the Jackson products. Just a few more thoughts to consider. Might not be relevant to your work at your shop.
As far as the working of the "auto darkening" features, I think the guys seem OK with either shield. By the way, we still have those Fibermetal shields in use in our shop...some of the older gents won't let go of that shield that they have had for decades that still works great. I don't blame them, as long as it still works.
John Wright