I need a clear information which one sounds better??
OPUS or WMA ??
I have a lot of songs in FLAC. I need to convert those files.
You should perform your own listening test (https://wiki.hydrogenaud.io/index.php?title=Listening_Tests).
https://hydrogenaud.io/index.php?board=40.0
Hydrogenaudio Terms of Service (https://hydrogenaud.io/index.php?topic=3974)
WMA is a more than 20 year old format that hasn't been developed in over 15 years. It's not likely to be the best at anything.
I mean, is WMA even better than "state of the art" mp3 at this point (which really hasn't advanced much if at all in the last 10+ years either)
Indeed, the best thing you could do is your own listening test at a given bitrate. As Opus is an open codec and developed actively and WMA is proprietary and not developed anymore, my advice is to not even consider WMA. But I am of course not familiar with you own considerations/use cases.
Opus is the best at low bitrates. At mid-high bitrates they should perform similarly. Opus is quite a standard today and widely compatible. WMA is pretty much dead and being phased out.
AAC-LC is a better choice.
(https://listening-test.coresv.net/img2/wma1c.png)
https://hydrogenaud.io/index.php?topic=102875.msg988476#msg988476
And Opus is even superior.
(https://listening-test.coresv.net/s/scores_by_tracks_en.png)
https://listening-test.coresv.net/results.htm
If your device only supports MP3/WMA, WMA is worth consideration.
If your device supports AAC, AAC is the preferred option.
It's your choice.
Why would an end-user encode to WMA by now? Must be if they have some hardware (an in-car unit?) that doesn't support anything else?
Even then I suspect you're probably better off with mp3