Difference between Flowchart diagrams vs. UML activity diagrams

What is the practical difference between using flowchart diagrams and UML activity diagrams? I have some thoughts, but maybe I'm missing an elephant in the room?

Flowchart diagram:

1. Widely used;
2. Easily understood by non-programmers;
3. Old?

UML Activity diagram:

1. Standardized;
2. Supports concurrency;
3. Less known syntax, but still simple enough.

For my case of ad-hoc documenting a particular block of application logic, I decided to go with the flowchart diagrams. More people in the company will be able to understand them.