So I have a SB3 12 m, but want to get a smaller kite for stronger winds.
Should I get a SB10m, which I feel is a little too close to the 12,
or should I get a CB3 9M.

I feel like the 8M switchblade is a little too small,
Im 90kgs - and mostly kite in Sydney......

How about the Slingshot Rev in 9 sqm?

probably stick with the same brand of kite , i think its better to have similar safety systems.