Question

which is easier to learn Japanese or Korean

Answer 1

both are equally difficult
if you can only choose one to learn
pick the one that you think would be most useful to you in the future :)

Answer 2

I've taken a year of Japanese and looked at Korean as well, and I can tell you Sleepyhead is right about this one. They're both difficult languages, and require a great deal of effort to fully understand. Learning Japanese really is like learning 2 languages - one formal, one informal - and multiple writing systems.
I don't know much about Korean, but they seem similar enough that those practical language problems would persist there too.

Pick the one that makes you happier. Japanese was hard work, but I don't regret a moment. :)