I don't think there's a bad choice among them (athough I've never ridden a KX125A5).
My clapped out YZ125E with 125G forks and a lengthened shock was the least-peaky of them, but lacked the outright grunt too.
Without looking too carefully at spares availabilty, it seems that the RM-N/T would be the easiest to get and keep at race spec, closely followed by the YZ125G.