Hey @codex.jo ,
I've been working with Laravel for about 7 years now, and I'll give you my thoughts on the question. Fundamentally, I stick to using Eloquent whenever possible, and only grab for the Query Builder when the situation/need is more easily handled with it, or cannot be fully replicated with Eloquent.
Eloquent is a fantastic Active Record implementation and ORM, which makes every day tasks a breeze to accomplish, seeing that there is no direct writing of any SQL involved.
Yet, sometimes you want to do something fairly complex and want to work out the fundamental logic details first. That's a good time to grab for the Query Builder, since it is more directly relatable to vanilla SQL syntax.
Conclusion - it's good to know both well in, in order to be able to assess when to use them.
Hope this helps you a bit.
Cheers.