if you wanna get technical,
ST barrier only absorbs things which are coming towards it. So basically if something is stopped even 1mm before ST barrier, it wont get sucked in.
Kamui absorbs things, it is like black hole, it can actually attract things towards itself.
But i am not really sure about this.Since i don't know if kamui can attract non physical objects like ST barrier, if it can then sure, it wins.