there is a lot of bullsh* talked about streaming bitrates imho, so I am not at all surprised if you cannot readily tell them apart.
The truth is that the better the replay system and environment, the more readily you can distinguish between low/high or no compression.
So a super quiet optimised room with a multi $10K's system can be extraordinarily revealing, but a car frankly is no such thing.
It is a noisy, acoustically horrid environment fitted with unbelievably cheap components sold at eye watering prices for what they are.
As a rule of thumb once you get to 192Kbps, you are going to need a pretty decent system to hear any differences, and frankly 128Kbps is barely a limitation for automotive audio.
whayever is going on with Spotify right now it feels more like 64kbps, it is that obviously poor. Slacker clearly is better at this time, if not perfect.