When judging Blender remember it is a 3D animation package, not a CAD programme.
Having said that, I find it just fine for modelling stuff for 3D printing. And I can edit STL files on it without a problem.
My interest in 3D printing and gorwing interest in paintball modifications/making stuff has gotten me to do a little bit more on the CAD side, but those CAD programmes you listed are Windows only so I do not use them and even if I did I am not qualified to judge like people here who have very likely used them to make actual objects. I just posted to say that I feel Blender is perfectly OK for STL creation for 3D printing.
Those online free as in beer CAD through a website creations are nifty technologically speaking but I in principle would not like have the files stored elsewhere and all web apps that are normally native apps annoy me anyway. That is just me though.
Did you look at OnShape?
You started by mentioning open source programmes. Just so you know in case it matters to you, Blender is the only open source programme of the ones you listed.
I installed FreeCAD. It seems to have good momentum, but it is not even at version 1 yet so it will be lacking. However, I look forward to learning with it a bit,