I think in your apartment complex you're probably affected by a bunch of other people who are keeping their curtains open in the day and not ventilating in the evening, so you'll be screwed whatever. Your trailer will have been roasting in the day, but will also have been small and so easy to fully ventilate.

I think your suspicion misses other important variables: for example, I might just live somewhere cooler than what you're thinking about. That's why I don't think this personal experience swapping is very productive.

In contrast, the science is pretty simple: all other things being equal, a building with high thermal mass will maintain the same average temperature as one with low thermal mass. You may well be more comfortable during the worst nights, but you'll be less comfortable during the worst days. But special attention to cooling sleeping areas that can be performed in any house can mitigate that, but can't mitigate peak temperatures.