I love all three of Seasun's step workouts.
I love complex choreography and crave workouts that are more complex than Cathe's. Seasun fits the bill.
Based on the fact that you've struggled with some of Cathe's stuff, you will probably need to watch Seasun a couple of times, then try a combo at a time and see how you do.
I think it is well worth it. Personally, I have never struggled with any part of The Next Step. I think it is cued very well, and moves flow, etc. etc. I like it better than Rock Steady Step and Straight Up Step, but I think they are all great step workouts and I use them all.
Netflix might have these available--you can try before you buy...
Good luck!
Wendy