I am not the right person to reply as I am new to the forum and storyline but I worked with presenter. However, from limited experience, there are some things that i find very helpful in storyline. Generally, I think you will get your interactive course out in a shorter time. See attached a slide summarizing a process build one one slides using layers in about an hour.
I can mention here a few of the things i find useful.
1) The time line allows me to do things much faster. I can move objects up and down and easily name and keep everything tidy. I can zoom on the time line, select a section of the audio, play that section and move other objects to sync them with the audio without much effort .
2) The layers panels allows me to hide objects in other layers but also to show a few layers out of many to help me place things around. The ability to use layers makes it possible to implement interactions without much thought.
3) If you think about a process in advance, its possible to use a lot of copy and paste work where you work some object and then copy its settings to other objects them make quick adjustments.
4) I find the review processing time, even for a whole scene is much faster in storyline as compared to presenter. It can save sometime in the long run.
5) I find the output for other devices such as ipad quite good but maybe they are as good for presenter. I did not try that before. I see that storyline offers a variety of other formats which give more possibilities.
6) Although i have not worked much with the storyline variables, from the much i have seen, I think this provides a big possibility to hold data for conditional processing.
That is part of my take on storyline, thanks,