I've actually stopped even trying doing A/B comparisons and instead rely on my reaction to the music over time. My system is also not at the same level as many on this forum and I'm not a quest to continually be unhappy and wanting something more.
Everyone has a limited ability to remember exactly how something sounded.
I've read that cables always require time to settle/burn-in to sound their best so a quick comparison isn't possible.
With the level of "everything matters" that people experience on this forum doing an A/B comparison is virtually impossible. Even with parallel setups using the same equipment, do we really believe that they are truly identical? Are they plugged into the exact same plug? They are using different inputs with slightly different signal paths. The sources are not in exactly the same location, so their relative positions to acoustic fairy dust is different.
Then there's the fact that different doesn't always mean better or work, sometimes its just personal preference.
If you've ever seen an interview with Jason from Schiit Audio, you may be familiar with his comment that after a couple of beers it's really hard to tell a difference.
Some of what I'm saying is intended with humor, but if you take everything you read on this forum it's not that far off from what should be expected.
Your son's presence could have literally changed the acoustics in your room resulting in a change in preference for you.
I think anyone willing to be open to confirmation bias and placebo effect will come to a point where it's impossible to truly know which is better. My standard is if I have to repeatedly A/B to form an opinion it must not matter that much.