All ch. stereo vs Studio mix?

Hello all, I'd like to know what's the difference between these 2 listening modes?
I got a ps3 connected through hdmi to my tx-sr 309 avr, and when playing music I was trying different options and found this one; I recently added rear speakers to my system and I don't think I've seen it before....
From what I understand.. All channel stereo outputs 5.1 channels, and studio mix does the same thing, but to me it sounds better, don't know why....

Anyone knows the difference it makes ?
Does it make each speaker play different parts of the stereo mix? Kind of like a "forced" surround mix?

Thanks in advance!

STUDIO MIX is suitable for rock or pop music, listening to music in this mode creates a lively sound field with a powerful acoustic image, like being at a club or rock concert. All Channel Stereo is ideal for background music, this mode fills the entire listening area with stereo sound from the front, surround, and surround back speakers.

Hope this helps,

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