Should common patterns be organized as L3 constructs or stacks in AWS CDK apps?

I started learning AWS CDK, and I found a L3 construct is a means to organize common patterns of building blocks;

• see the constructs composition to form higher level construct illustrated here

At the same time, CDK stacks are equivalent to Cloudformation stacks, and stack is also a unit to form composition (through nested stacks), which is typically a resuable unit of AWS components;

• see the nested stack composition illustrated here in the cloudformation doc;

Now I have the question when we should build L3 construct as reusable patterns solutions and when we should build stack as reusable patterns solutions.