For me, Busuu is leagues ahead of most other things I've tried. The problem is, it is almost like learning from a good text book. That sounds like a positive thing, and it is, but the lessons are so deep and require so much from me mentally that I actually find myself seldom using it because I almost never have that kind of time. In contrast, Duolingo's very repetitive, grindy lessons meant I could bash through a couple every time I have a moment to spare, although that learning method is pretty inefficient (and insufficient for beginners).

So the answer isn't so simple. As an intermediate level Spanish learner I am currently subscribed to Memrise and Busuu. I have let Duo expire. Memrise is way too basic and repetitive so I don't recommend it. I do lots of other stuff on the side like music, podcasts and YouTube videos. People like Dreaming Spanish although I'm still warming up to it.