I would think the reogenerator would be better strictly speaking from a stats point of view, faster charge more health more resistance the only difference is the capacity.
I’m not sure how powerful enemies are at lvl 70 so I can’t say for certain which one would fair better at your level since I can’t gauge how low the capacity really is on the reogenerator.
Since it’s about half of the other I am guessing the shield doesn’t take very many hits before it is drained so I could see where the capacity of the reogenerator would require some skill in avoiding getting hit to recharge.
I would imagine this would be why the reogenerator wouldn’t be optimal in situations where not getting hit is impossible.
If you could get a class mod that adds to the shield capacity the reogenerator could be better suited.