BS2 is better for perc sounds IMO. You can get good kick/snare/hat sounds out of it, which is fun. It also does all the standard synth patches nicely, including SH-like sounds and Moogy bass. The multi-mode filters make the synth really versatile overall.
Korg is probably better for drones / long evolving patches though. Those VCFs are really wild too, which the BS2 can't match. The BS2 is 'polite' most of the time, whereas the Korg wails. MS20 can do more with external input sounds, if that's your thing.
AFX mode on the BS2 sends the synth to the next level, it's got memories, and it works well as a MIDI controller for a DAW too.
It can do OSC sync sounds, which you can't do on the Korg.
Really good value if it's your only/main monosynth.
For a partner synth that complements the BS2 well, I'd recommend the Behr Neutron.. or the MS20FS / K2.

K2 has better build quality than the MS20 mini IMO.