I'm not an expert, or even close, but I have a couple of comments.
1. AFAIK it's the frequent restarts of the older unit that consumes the most power. So I think you will get better results over a longer period, say overnight.
2. Using 2 units in one room at the same time. How can you know which unit was more/less responsible for the drop in temperature. Is it possible that the new unit was working harder to get down to the set temperature?