I tried the spiraling out today. I found it increases more stabilisation (core) & literally eradicated any twisting/core rotation, made me more solid.
Done a little background research on the BOSU. 
Significantly works the (TA) transversus abdominis muscle & inner core. (Hodges & Richardson 1997b) and found that during unilateral leg/arm and limb movements, the transverse abdominis was the first muscle activated, leading researchers to believe that the transverse abdominis must be “pre-programmed by the central nervous system”. It’s one of only 4 muscles (pelvic floor etc) ‘directly’ linked to the CNS by all accounts.
Those key muscles ‘generate’ power before the legs/arms. Certain BOSU exercises (I found 4) overload the “generator”. The instability factor of the ball actually leads to a further increase in the activation of these muscles.
But more significantly, the “generator” doesn’t get worked at the squat rack, performing oly’s etc.