Stolen bikes

chains (goo wuality) - wirecuters (5 sec)
wire(good quality) - wirecutters (5 sec)
d lock (good quality) - angle grinder (at least 5-10 mins, plus a lot of obvious noise)

i dont need to say any more.

its not the material, it's the technique.

chains allow for locking to more varied objects, if you keep your chain tight and off the floor, you won't get through it in 5 seconds with wire cutters. you need bolt cutters, and the leverage of the floor and body weight to get through. take those fabric sleeves off your chain when you buy it, and chain the bike up as tight as possible.