I have used the upgraded ST card and the game card for some weeks now
(and before that, the 2 older ST card, high and low gain)
The upgraded ST (wich I prefer not to call "V2", has older ones already have V2.0 printed on the circuitboard) is for sure an improvement. It also has a quite different sound signature. The older ST is slightly on the warm side, the new one is much more "flat", with firmer bass and extended / thicker highs.
Comparing with the game is more difficult and I'm sure it will be a matter of taste and adequation with your IEM.
To me, the Game card sound signature is more like the old ST, but it delivers it in a more musical way, with greater details, control, and definition.
After being quite supprised by the performance (and new sound) of the upgraded ST, I'm back on the Game card now, for it's more "delicate" sound.
If you like classical music, jazz, accoustic music and the sound of true instruments, the game would probably be your choice.
If you prefer a more flat and forward sound at the expense of a slight boldness, the ST is for you
Well, just my subjective impressions, it may also vary depending on your IEM.