I prefer the sound of a single BS2 to a single Balance.  However, I absolutely love my stereo paired Balances.  I have not heard a stereo pair of BS2s, but I was concerned that the side firing midrange drivers wound mess up the stereo.  I can't really put to words why I have these preferences, but I hope this helps.

Your BS2 has GVA?  Gen.3 will not.  Balance still GVA-optional.

I have the MK1 BS2 and think it’s wonderful, though I’m not sure I can justify replacing it at the new price. It’s over a grand more than what I paid for mine! My MK1 BS1 though is sounding a bit rough these days and I would consider replacing it, so I hope that an updated version is in the pipeline. GVA was not something that appealed to me so I’m glad to see that function has been removed.  Who wants a house full of microphones anyway.

I had 2 Balance stereo paired. They were great. Sold them with the sale of my home. Bought one Gen3 Beosound 2 to use while in a temporary house while construction of new home. Liked it so well I bought a second and Paired. They sound awesome. There is still clear stereo separation but where you are in the room is not important. Good sound all over. They do not play as loud as the paired Balance units so if you really like extremely loud music or have a really large room you might prefer the Balance.  My room is about 16’ x 30’ and I find there is more than enough volume.