My first real blind test was years ago, you can search it on AVS forum LS50 vs Revel M105, I too couldn't tell a difference initially, they both sounded great. It wasn't until I attempted to test them similarly to the Harman method that I could easily spot differences, IE level matched, 1 speaker of each in mono, able to instantly switch back and forth and I was blindfolded. If you are simply swapping out speakers and playing a few songs and declaring no difference that isn't the way to do it, there are too many biases at play and our audible memory is too short, check out the thread from Dr. Toole on evaluating speakers in mono for more on this.
Once I did that proper comparison I was easily able to pick a winner between the 2, every song was unanimous and it took less than 10 seconds per song to tell a difference, it was much easier. You might need to do the same thing and I'm sure your results will change.