They are entirely different tools - and both are not very good at promoting Youtube videos.
While links count - the first thing I'd do is get views, comments, likes etc.
Install Vagex (free) and use that, then later maybe consider GSA for some links
Scrapebox's forte is SCRAPING - it also has the ability to be programmed to post to many more platforms than it has on start up. It can't be used to program complex sites - but it can do many more blog style sites and some others than are prgrammed into it.
However, GSA is the better linker - but if Youtube vids are your target then linking is a secondary consideration, you rank youtube first with views, likes, subs and comments.
In some niches you don't need a single link to rank a Youtube vid in Youtube, and when you are promoting a product through Youtube then most of your viewers will come directly through Youtube rather than Google search. (They are both Google of course - but you know what I mean)
Scritty