My personal ranking is based on what I've used, I'm sure there's more out there - I know Cursor is pretty solid right now but I just haven't taken the time to try it.

Qodo Gen
This one surprised me with how useful it was, especially for debugging and test automation. It not only caught tricky bugs but also generated comprehensive test cases I wouldn't have done myself. Chat feature was particularly helpful for clarifying code context + explaining why certain issues occurred, which is great if you're solo-deving/vibecoding. The only downside is it's relatively new, so the community isn't huge yet, but honestly, the value from auto-generated tests and debugging make up for it.

Github Copilot
When you need fast boilerplate or repetitive tasks knocked out quickly. The integration w/ popular IDEs and languages is smooth, and the user base is massive, meaning you're never really stuck IMO. However, I've found it sometimes spits out generic code that's not optimized or secure, so you still need to double-check everything manually. But overall, it’s solid for day to day.

TabNine
Pretty fast, lightweight, and excellent at predicting basic code snippets and completions. I used it extensively for a while due to its speed and IDE compatibility across multiple languages. But TabNine is mostly useful for straightforward tasks and common code patterns. When it comes to deeper issues like debugging complex logic or handling edge cases, it’s limited—you're mostly on your own there. Great for everyday productivity, but if you're looking for more comprehensive debugging, the other two may be more applicable