Should I use more than one AI model?
For any answer you are going to act on, yes, use more than one AI model. A single model gives you one confident answer and no way to know if it is right, because a correct answer and a hallucination look the same. Two or three different models, asked independently, catch errors one model misses and show you exactly where the question is uncertain by where they disagree. For quick, low-stakes, easily-reversible tasks, one model is fine. The moment being wrong has a cost, a second and third model is the cheapest insurance you can buy.
When one model is enough
Not every question needs a committee. If you are drafting a casual email, brainstorming, or doing anything where a wrong answer costs you nothing and is obvious the moment you see it, one model is the right tool. Adding more would just be friction.
When one model is a liability
The line is reversibility and cost. If being wrong is expensive, hard to undo, or hard to even notice, one model is a gamble. You are trusting a system that sounds equally confident when it is right and when it is inventing a company out of thin air. In a run on this site, one of five models did exactly that, and the only reason it got caught is that four others were in the room. Read the run.
How to use several without the hassle
You do not need to be technical. Open two or three chat tabs from different providers, paste the same brief into each, keep them from seeing each other's answers, then compare. Free tiers are enough; see do I need paid AI subscriptions. The disciplined version of this is the Council Method, and the free Council Protocol is the copy-paste script.
The full method is in Let the AI Be Smart.
Go deeper: this site's hub page on the Council Method is the full definition. Related questions: Why do different AI models give different answers to the same question?, Do I need paid AI subscriptions to use multiple models?, What is the Council Method?.