Chemically the two are the same, "kosher salt" is not strictly speaking the correct terminology, and "which melts the fastest" is sort of the wrong question to be asking anyway.
That said, I would expect table salt (which is usually in smaller particles) to melt ice faster than the relatively larger koshering salt.
Table Salt.
A serous difference doesn't exist.
Kosher salt
The densiity of kosher and table salt is NOT the same kosher is significantly less dense than table is because of the fluffier crystals.
Yes, you can substitute table salt for kosher salt in a recipe, but you will need to use less table salt because it is more concentrated than kosher salt.
No, kosher salt is identical in mineral content to table salt.
Any serious difference exist between kosher salt and standard table salt.
"Kosher salt" is chemically the same as regular table salt, sodium chloride. It's not that the salt itself is kosher (it is, but so is just about any pure table salt). It's really more "koshering salt" ... suitable for use in salting meat to make it kosher (by removing the blood). Kosher salt is usually physically, not chemically, different from regular table salt. The grains tend to be larger and in the form of flat flakes rather than tiny cubes. Kosher salt usually contains no additives such as iodine (regular table salt is often sold with added iodine, usually labelled "iodized salt").
Yes, you can use table salt instead of kosher salt in this recipe, but be aware that table salt is more concentrated than kosher salt, so you will need to use less of it.
Yes, table salt can be substituted for kosher salt in a recipe, but you will need to use less table salt than the amount of kosher salt called for in the recipe due to the difference in saltiness.
Table salt and kosher salt are both 39% sodium by weight.
A suitable substitute for kosher salt when baking is table salt.