textbooks for self study? (sogang, ttmik, integrated korean)

i am starting my third year of korean at my university, and we have used the integrated korean books up until this point. i really enjoyed the pace and amount of practice those books have offered, but instead of continuing onto high intermediate 1, we are switching to sogang 3a.

i was wondering if sogang is higher quality than integrated korean, for anyone who has tried it? should i continue with integrated on the side for self study, or is it useless after intermediate 2? and how about ttmik?

i guess i'm just asking for thoughts on these three textbook series, what is the most helpful and worth studying outside of class?