If you're interested in combatively realistic swordsmanship, though, you should be aware of one thing. The martial arts taught by Shim Gum Do are not historical Korean combat arts. Nobody has ever used Shim Gum Do swordsmanship on any battlefield. These arts were revealed to the founder of Shim Gum Do in a religious vision.
I don't question the validity of the founder's vision. Many Japanese sword arts were created in the same way. However, the founders of those arts had been training in combatively-proven forms of swordsmanship for years or decades prior to their visions, and in many cases they had extensive experience of battles and duels. One can assume that whatever insights the vision gave them were filtered through their established understanding of combat reality. The founder of Shim Gum Do had no such experience or training as far as I have been able to determine. Therefore, while Shim Gum Do would probably be a very rewarding way to practice Zen, it is probably not a way to learn realistic swordsmanship. Since realistic swordsmanship is not needed in the modern world, this is strictly a matter of personal taste and temperament.