Woah, I would’ve never guessed they were the same. Thank you.In my experience, Rotala indica is a bit more rare than Rotala rotundifolia. In fact, I have bought several plants labeled as R. indica over the years, but I've only ever received R. rotundifolia. This is not really a concern, as R. rotundifolia is one of the hardiest, most forgiving stem plants out there.
The reason it seems like you're seeing two different plants is that R. rotundifolia looks completely different in different conditions. It has rounder leaves when grown out of the water, and is more red and compact in high light.
R. indica changes too, but not so much. It keeps rounder leaves, even under water. And, it stays a bit greener, even in high light.
Your first picture could be either plant, as they look similar in their emersed state. But, the plant on the right is clearly R. rotundifolia.