<font color=blue>I like the solar one, since you can leave it out to recharge</font color=blue>
The Jackson website says, "<font color=blue>Solar-assist panel extends battery life</font color=blue>". I can't find any more detailed information at the website. I know you posted on a Miller helmet, and maybe the Solar/battery features are different on that model.
My helmet does not have rechargeable batteries. It still has the original AAA Rayovac alkalines that say "do no recharge" right on the battery. I have read posts other than yours suggesting that the Solar feature "charges" the batteries. I don't think mine does.
I believe the "Solar assist" just picks up some (or all) of the electical requirement of maintaining the lense shade from light generated by the welding arc. When not welding, a lighter, sunglasses type shade is present on my helmet, for 20 minutes anyhow, until it turns itself off. Solar assist from ambient light and battery power is probably needed to maintain that shade. However, the solar panel must be pretty effective for little AAAs to last three years. I don't think, however, the Solar panel charges the batteries, at least on my helmet. Does anybody have rechargeable batteries in their helmets?
OkieG