Your data-saving test was probably limited by how fast you could save to disk a roughly equal amount of data with the two databases; queries might work and perform more differently.
I also simply inserted and read the data, no complex queries or anything. Key-value store is all I needed and for this particular case PostgreSQL was as good at it as Redis.
And once you implement a global map which is accessible from multiple processes, you might as well use an existing solution, like Redis. Or, as I've learned, pgSQL - which gave me the same performance with less moving parts (because I was already using it) when I disabled WAL.