Nobody became ill after the trip.
You're right, the units weren't used in the same water. My suspicion is that some of the water we used, perhaps the water that was taken from cow-contaminated sources, would have made us sick. My understanding is that the incidence of backcountry water-acquired diarrhea is 3-5%, so it's always hard to say....
The point of the article was comparing the two devices for use in long distance hiking, commenting on the things long distance hikers tend to find important: convenience, cost, maintenance, etc. The two units provided the same level of water safety if your criteria is that none of us got sick. The two devices do differ in what they do and do not filter. more on that in another comment.
I personally view battery changing more as a convenience feature and maintenance as something that's done on a routine basis to prevent damage or operating failure. Yes, the SteriPen won't work if the batteries run out, so maybe this is just semantics.