I was curious about Lead-bismuth eutectic, so had a look on Wikipedia:
As compared to sodium-based liquid metal coolants such as liquid sodium or NaK, lead-based coolants have significantly higher boiling points, meaning a [nuclear] reactor can be operated without risk of coolant boiling at much higher temperatures. This improves thermal efficiency and could potentially allow hydrogen production through thermochemical processes.
Lead and LBE also do not react readily with water or air, in contrast to sodium and NaK 
which ignite spontaneously in air and react explosively with water. This means that lead- or LBE-cooled reactors, unlike sodium-cooled designs, would not need an intermediate coolant loop, which reduces the capital investment required for a plant.
Best not try sodium and NaK then 
