PSA: Try FreeCAD Link Branch (it's a big improvement!)
Recently I've been having feelings about moving away from Fusion 360. The combination of cloud app / filesystem and their demonstrated willingness to remove features and add arbitrary limitations (eg. 10 editable model limit) makes me feel uneasy about using it. To be clear I'm grateful that AutoDesk provide a free license at all, and it's an incredible piece of software, but I have a sense of vulnerability while using and honing my skills in it. If you've ever rented a house you'll know the feeling - you quite don't feel like it's really your home, if the landlord wants to make renovate or redecorate you don't have any choice and you could be evicted at any moment.
So I tried FreeCAD. At first, I have to say that it felt a little like stepping out of a spaceship (Fusion) and banging rocks together like a caveman. It's not that you can't do (most) of the same things as an enterprise CAD package, but the killer feature of Fusion is the level of intuitiveness and "it just works" that makes FreeCAD seem like trying to write Latin.
After a week of on-and-off learning I was not sure I wanted to continue. Even after getting comfortable with the basics, frustration levels would spike to 11 sometimes. The main issue I kept running into was that altering a previous feature would break everything that came after, requiring a varying amount of work to fix. The FreeCAD wiki suggests ways to mitigate this but many of them are un-intuitive and/or inconvenient. After some googling this seems to be caused by a pretty difficult to solve issue called the "Topological Naming Problem" (where FreeCAD can't keep track of surfaces / edges / vertexes in a stable fashion when features are changed). Then I came across this blog post that pointed out a fix has actually been developed earlier this year. A developer by the name of RealThunder has created a fork of FreeCAD called "Link Branch" which can track topology in a (more) stable fashion.
I tried this branch and was blown away by how much more usable it is. Not only can it handle changes to past features almost perfectly, but I can create multiple bodies from a single sketch (not possible before) and there are other UI tweaks that make creating features easier such as the ability to preview fillets and chamfers at the same time as selecting their edges. I'm not totally sure which of these features are unique to Link branch vs which might be pre-release in the main branch, but certainly the topology naming fix is unique to Link.
So if you have tried FreeCAD in the past and been frustrated, or if Fusion's past free license changes or price increases are making you uneasy, give the Link Branch a try! Downloads are available in the releases page.
Personally I see blender more as an animation or organic modeling tool whereas CAD software like fusion is better when you need exact dimensions for your parts
CAD Sketcher improves Blender a bit, but it's still not good enough to turn Blender into a dimensionally accurate CAD, and I found the UI to be fairly clunky and if anything even less intuitive than FreeCAD, honestly.
So is there an open source direct modeler? I've been working in Designspark, but while it is not currently as onerous as F360 or OnShape (god forbid I stumble into something that other people decide might be worth a few bucks), it's still a (free for now) subscription and has had feature erosion, specifically importing darn near anything pre-existing. I'm not making anything complex enough that it suffers from the Direct Modeling workflow, and I find that workflow much more intuitive. Shoot, I'd even settle for a fork of Solvespace with chamfers and fillets, LOL.
I haven't used Blender for this purpose (or FreeCAD at all, for that matter...just OpenSCAD for doing models for 3D printing). But it looks like Blender has some sort of add-on support for parametric modeling that's being worked on.
A constraint-based sketcher addon created by hlorus for Blender that allows you to create precise 2d shapes by defining CAD geometric constraints like tangents, distances, angles, equal and more. These Sketches are then converted into beziers or mesh which still stay editable through a fully non-destructive workflow i.e, Geometry nodes and modifiers.
It's not, historically, the main purpose of the software, but maybe Blender will ultimately wind up moving into the CAD world too to some degree.
How does graph paper stack against a canvas? One is for engineering, the other is for art.
Also, FreeCAD is at least a decade behind Blender in the "No it's actually really good now and is actually being widely adopted in industry" department.
I know a bunch of people already told you that they are not the same program, but this is the way I always think about them:
Blender is like modeling with clay. You mold it, push it around, and stick more pieces on here and there.
FreeCAD is like modeling with building blocks. You measure the part you need and select the block's that build that part. You can also swap out blocks for different blocks at any time.
Blender is a swiss army knife, not really comparable, but i'd recommend it over most CAD software if your main focus is 3d printing as most slicer convert to mesh data anyway.
Im not going to try and convince people who have already made their mind up, but I ditched Fusion for Blender ages ago and haven't looked back. Its completely usable for CAD and precision design for 3D printing or what have you. Its not built for it, but its capable if you learn how.
The lack of pure CAD focus is a drawback, but it is largely made up for in blenders absolutely amazing general purpose tool set. Its not just mesh manipulation, with geometry nodes you can create complex intricate shapes that are also precise to your requirements. There are countless workflows and plugins that allow you to make blender adapt your needs. You can remix existing STLs and bring in reference photos/models/etc. Simply put IMO there is no need to use any other program for almost any aspect of 3D design, and so it has become my go to.
I don't recommend it for beginners, but it really is an incredibly powerful tool if you put the work in. Is it better that FreeCAD or Fusion? I am not qualified to say, but I'm pretty confident there are few features either package has that blender does not.
My experience in trying Blender for 3d printed part design was short lived because it's not really built for doing accurate and precise modeling, where FreeCAD is.
Blender is well received in the industry and can compete with the best. It also has a few nice features that aren't standard and make it stand out among the competition.