There are online test you can do to see if you can successfully identify the FLAC from the MP3. I did one and failed miserably.

They say that if you have a very good DAC, amplifier and speaker / headphone system (as well as a good ear for audio), that you can hear it. But I would do the test first to see if it applies to your situation.

It is better, but it depends on the audio for the difference. Also, it would probably be hard to hear the difference playing over a phones speakers. The weakest link in the chain is always the problem you notice the most. Having a good setup for amp/speakers and you can hear the difference. Using Bluetooth earbuds to mow the lawn, it doesn’t matter. Sitting in my living room on my nice stereo, I notice.

It could be the quality of your headphones.

I'm not an audiophile, but back-in-the-day I bought some analog "sennheiser studio monitors" as opposed to "just headphones".

I actually returned the first one and exchanged them, because when I listened to a live recorded CD, I kept hearing loud "pops" that I didn't hear with my "regular headphones". I assumed they were defective.

The exchanged sennheiser had the same "pop" in this CD. It turns out, most "regular headphones" didn't have the same depth in sound frequency as studio monitors and the "pops" were accidental artifacts that were mixed into the CD.

For other CD's, I'd hear telephones ringing and sirens in the background.

Eventually, I got use to it. Then after a few years, I replaced my CD collection with mp3's... and I could tell a different in songs/albums I was really familiar with. The base wasn't as deep, the high sounds weren't as high, I didn't hear telephones ringing in the background.

I had the same sennheiser, it was just that the nature of mp3's "flattened" the music.

Now, with Bluetooth and the disappearance of 3.5 mm jacks, there are too many layers of digital conversion happening. I've given up... and now just have some cheap ear buds I listen to.

Flac files contain orders of magnitude more data. As for the listening experience it's only ever going to be as good as the speakers at the other end. You'll also need a wired connection to said speakers in order to avoid some compression over Bluetooth. (Unless there's some newfangled lossless BT protocol that I'm unaware of.)

yeh

Go to Opus 128 kbps. About the same as MP3 320 or better.

The space it takes up is negligible in the modern era of cheap SSDs (and even cheaper hard drives).

The main benefit is not in being able to hear a difference from 320Kbps mp3 (I know I sure can't), but knowing that you can re-encode the file as many times as you want, without any quality loss (assuming you're going from lossless to lossless, of course). Or create an mp3 from the flac file at any time, with the same quality as a ripped CD.

So basically FLAC is great if you produce/edit/re-encode your music files often. If you don't do any of that (and have no plans to future-proof your music collection), then 320Kbps MP3 is more than adequate for your needs.