I'd think Trello and Asana are much closer competitors. JIRA is like an over engineered spaceship with more features than anyone could learn in a lifetime. Comparatively Trello functions more like a Prius. Priuses and spaceships don't compete.
JIRA shines in areas that (a) have workflow and (b) require repeatable processes across a number of people.
Once you have 20+ people on a project, you need repeatable processes.
In cases like bug tracking, project management, customer service, help desks, HR onboarding and hundreds others you need workflow.
Trello shines in areas where you have (a) small teams or (b) require ad-hoc semi-structured data.
In small teams, even if repeatable process would help you, it's not worth the cost of setting up a system - you achieve it by social means.
Trello also has many, many use-cases where you want to start something quick, or personal. In this case it really shines, with near-zero friction to get started.
Scott, CEO Atlassian
But the folks who have a working process and a large number of people and teams are usually complaining the other way round: that no tool supports their workflow. Which is where JIRA shines. I don't know another tool that can be configured to such ridiculous detail.
The Trello acquisition makes total sense because it fills in that gap that JIRA is bad at.
You might not view them as that, but they are, well were.
Don't get me wrong – I like them both. When I have to plan out personal projects, Trello is great. During the day, we use JIRA. The use cases are different, and the products are both suitable. I'm madly bemused that people look at the very, very surface layer of the UI (oh look, it has cards in columns!) and assume the products are the same.
In the Innovator's Dilemma sense, absolutely.