I know a couple of you out there saw this already, but what a nice surprise to find that this movie was on Netflix! (That's great for us because I don't care for most of the streaming sites like dramafever and almost all the good download sites have been stupidly shut down) I had read reviews that said the first half of the Roaring Currents movie was slow, but I didn't find that to be the case at all, especially since the Yi Soon Shin series had over 20 episodes of his boyhood! I can't say either the series or movie is better - I loved them both!
Overall, this is one of the very best Korean movies I've ever seen, certainly the best historical one. Here's the link (you need to be signed in to Netflix): www.netflix.com/title/80011706
I saw this a while back and really loved it. I was browsing at my library and just happened to see the DVD on the shelf and checked it out. It was really cool that they had a Korean movie there. The only thing I didn't like was that it was dubbed, not subtitled.