Obj vs blender file while saving assets so i'm trying to figure out the best way to manage my project, especially my assets (library). I see I can export my objects as obj files and import them wherever I need them. I also have seen people recommending to save all assets in a single blend file, and the third I've seen is saving each model/object in its own blend file. I am confused as to which way should i store my assets. Right now, i have couple of rigged characters, trees, cars, road, mountains, night sky, clouds and a moon. 

UPDATE: I am working on making a small series of animated videos, each 4-5 minutes long. Assets could be used in different scenes of the same video as wells as in other videos. I am curious to know the pros and cons so as to decide which option to chose.
OBJ (along with other most formats) are interchange file formats, generally meant for cross application data transfer, like importing and exporting between software, not a reliable way to save data.

You should only use them if you plan on using your assets elsewhere in an application or software that can't directly read .blend files.

Saving your assets in a format other than .blend will invariably result in data loss. At the very least materials and textures, but in most cases also modifiers, rigging and any other Blender specific data, along with animations, constraints, simulations among others.

You also can't dynamically link data from objects and easily reuse it, once imported it becomes static local data, removing any benefits of shared libraries like an always up to date central file used across all projects, or automatic update propagation, especially useful in multi user environments.

OBJ should be used as an interchange file format, not a long term storage solution for a project or library file.