I actually was using the Heavy Rotation eyeliner since summer, I bought it in Korea, so it`s a repurchase! (^0^ ) It`s a nice soft black pencil eyeliner and it doesn`t crease, etc, stays in place all day. ^^ The B&C is thinner and more hard and deeper black! It`s staying power is ....scary. XD A real heavy duty eyeliner.
B&C very thin / Heavy Rotation thicker
top: B&C / bottom: Heavy Rotation
B&C is blacker as you can probably see even though I modified the photo and you can draw a really thin line. Heavy Rotation is thicker but more comfortable for tighlining for example, because it`s also softer. The pencils are also packed with moisturizing / care ingredients like wax or hialuron. I could buy an eyeliner from Dior or Chanel, but tbh I prefer the japanese ones, they are always super reliable and really affordable too. And I`m too old to care for trying out local drug store brands eyeliners, they always crease and give me panda eyes. :P
So yeah, if you`re looking for a good black pencil eyeliners, I recommend the above! If you want deeper black and thinner - B&C, if you want a typical pencil size and soft one - Heavyrotation! ^^