Spinor condensates constitute an ideal system for the study of magnetic superfluids. Collisions induce a coherent transfer between Zeeman sublevels (m), which is especially fascinating in condensates initially in m=0. In that case creation of EPR-like pairs of atoms with m=+1 and m=-1 is ideally purely triggered by quantum fluctuations, resembling a parametric amplifier. This correlated pair creation presents an intriguing and up to now not fully understood dependence with the applied magnetic field. In the first part of my talk I will show how the pair creation efficiency reflects the confinement-induced magnetic-field dependence of the most unstable Bogoliubov spin excitations of the trapped condensate. I will discuss how this theory describes very well recent experiments in Hannover. In the second part of my talk, I will present recent theoretical and experimental results on the nature of the triggering of the spinor dynamics, showing that depending on the applied magnetic field, this dynamics may be either extremelly sensitive to classical noise, or purely given by quantum vacuum fluctuations.