Cold Front: -60% Move Speed
Mystic Slow: 30% Movement Slow
I think its better to have all slow reduction as "Movement Slow" as its easier to differentiate between items for gaining speed and reducing enemy speed when using the search function in the shop.
Edit: So do Slowing Bullets, Slowing Hex, Point Blank, Sharpshooter(?), Lifestrike, Capacitor, Cheat Death(?), Colossus, Phantom Strike and Vortex Web.