> I am actually quite interested to see how clear their data / recommendations would be, but haven't had the time to do so yet.

I have tried both, and while ahrefs probably has a better dataset, semrush does very specific recommendations when it comes to link building for example. They will suggest what sites to contact to ask for backlinks (something I have not yet tried, because other people email me all the time asking for backlinks or guest posts so I know how annoying it is).