Most people pick one tool and use it for everything, which is reasonable and also leaves a lot on the table. The gap between the right tool and the wrong one for a given job is frequently larger than the gap between a bad prompt and a good one.
A rough division that holds up. Long documents and careful writing: Claude. Anything where you need the sources and want to follow them: Perplexity. Work that already lives in Google Docs, Sheets or Gmail: Gemini. General purpose default with the broadest set of connections: ChatGPT.
The reason no vendor will tell you this is straightforward. Every one of them publishes free training, all of it is good, and none of it can say that a different company's product is the better choice for the thing you are about to do.
The lesson this comes from
Choosing between the four tools
Two tools, side by side, in about ninety seconds of actual asking. Not a review. A test you run yourself, on a day you choose, which is the only version of this comparison worth trusting.