When I started using the LLM while coding, I was using Claude 3.5 Sonnet, but I was doing so with an IDE integration: Sourcegraph Cody. It was good, but had a large number of "meh" responses, especially in terms of autocomplete responses (they were typically useless outside of the very first parts of the suggestion).
I tried out Cursor, still with Claude 3.5 Sonnet, and the difference is night and day. The autocomplete responses with Cursor have been dramatically superior to what I was getting before... enough so that I switched despite the fact that Cursor is a VS Code fork and that there's no support outside of their VS Code fork (with Cody, I was using it in VS Code and Intellij products). Also Cursor is around twice the cost of Cody.
I'm not sure what the difference is... all of this is very much black box magic to me outside of the hand-waviest of explanations... but I have to expect that Cursor is providing more context to the autocomplete integration. I have to imagine that this contributes to the much higher (proportionately speaking) price point.