Create model as single or multiple meshes?

I’ve made a barrel model in Blender using different objects like base, rings, infusion etc. Should I merge these objects into single mesh, parent them into one object or keep them separated for use in Unity?

Parenting objects together allows me to set casting shadows by barrel base and not casting by rings (rings tend to produce shadow artifacts) which gives me more control. How does it work out in the long term and what is a good practice to use?

It would work better and probably be lighter on resources to use one mesh. But it would be easier to make it break apart realistically if you keep them separate.
To sum up, it depends on what you need.