There's a massive flamewar going on on Russian forums on which system sounds "pro" and which has a "chinese walkman" sound.
Linux users arguments - since Vista you don't have true hardware DirectSound, instead you have crippled software mixer which does mandatory resampling and frequency cutoff, and doesn't allow any hardware effects such as CMSS-3D. We have our uber-kernel with ALSA, which has all the best drivers built-in and sounds like a studio system. Yes, you have WASAPI-exclusive, but it's still "processed" and so on...
Here's the link which shows XP and Vista-7 sound system differences - http://habrahabr.ru/blogs/sound_and_music/115092/
(which is used to tell that windows has the "worst sound ever")
Windows users arguments - you linux guys have some half-baked amateur placeholders instead of full-featured vendor drivers and a complete mess in sound frameworks, which results in muffled sound in and geeky under-the-hood tweaking in search for a "perfect sound".
Personally, I did find the Winamp sounding much better when I switched it to OpenAL output plugin from the default DirectSound on W7. Ableton provides the best quality I ever heard with DirectSound.
Well, of course no sane person believes some made-up holywar claims, so I want to hear an expert opinion on the subject.
It's not always case windows 7 sounds better than Linux ALSA or vice versa.It most importantly depends on driver.Linux does have vast support for sound drivers and now Windows 7 have good support too.I noticed in Linux although sound is not that loud it's more clearer and more natural.Well that's my opinion but yeah windows do have louder sound.