Short question,
given that our project is a 3D randomly generated mobile game, with all the meshes done in Blender and then assembled in different Unity prefabs, what would be generally better:
1 - A single object for every .blend file.
2 - Multiple objects inside a single .blend file.
I’m asking because I only find very old advice online.
Thanks for any help
generally better is vague
If the objects are static - multiple in one - preferably with only one texture would be good. If any are animated or rigged - I’d go for individual imports. No need over complicating the process of managing numerous rigged components in Unity by attempting to import them together.
just my 2cents.
For complex or rigged meshes, what theANMATOR2b days.
For static meshes, both will work.
However, you’ll probably have an easier time updating and managing your prefabs if you import them as single meshes from individual files.
Besides storing them in multiple .blend files, you have two more options (in case editing only one .blend file would be easier for your workflow)
Export to FBX with only one object per file. Blender’s FBX exporter has an option “Only Selected Object(s)”.
Create other .blend files that each Link (Ctrl+Alt+O) to one object in your master .blend file
Thanks for the info guys, I left my question vague, just to better compare the advice with my own experience. however this was what i experienced up to that point:
I tried linking child blend files to a master blend. I found that some times it does not update the child Blend automaticly. I then have to open every file manually and make sure it updates, then resave.
On the other hand, if i use multiple objects inside a single Blend, and then I put these objects directly inside a prefab, problems with autoupdating the prefab occur, at every new save. The Prefab gets messed up for reasons i do not understand.
If you let Unity directly import from .blend files, Unity will not know that the child .blend files need to be reimported, too. I’m not sure if a custom asset importer could trigger the reimport of another asset. It may be a necessary evil to trigger a manual reimport in this case (selecting multiple assets in Unity and clicking ‘reimport’ does work, though).
There’s also the option of doing a scripted export to FBX (even selecting individual objects in a .blend file for export is possible from script), which means all children are refresh when the master is changed. Scripting this is not too difficult I happen to have a script sitting that does it in my current project’s folder, so if you want to take this route, just hit me up 
I don’t know why having multiple objects in a single .blend file should cause problems for your prefabs. Can you describe your workflow and how they get messed up? Are you exporting selected objects to FBX in Blender or are you building prefabs by pulling individual objects from a .blend file in Unity? Do ‘messed up’ mean meshes go missing?
Well, I just figured it out that for static objects having a single blend file is the best option because your single blend model will have less size (almost half) than the combined all single files.
hope this helps someone 