Just inherited a "legacy" Salesforce Apex class that's basically a 2000-line god object with variable names like `a1`, `a2`, and `doProcess()`. Needed to figure out what it actually does before we can even think about replacing it.
Tried both Copilot Chat (in VS Code) and Cline's chat side-by-side. Task: explain the core logic and identify the main business rule buried in the nested loops.
Copilot Chat gave me a polite, high-level summary that was basically a re-statement of the method signatures. It was useless. Like getting a sales rep to read the feature list back to you. Had to drag it kicking and screaming into the actual mess, asking three or four increasingly specific prompts to get it to trace through one specific path. Even then, it hedged.
Cline was blunt. First response was "This is a discount calculation engine with a broken fallback pattern. The main rule is on line 847, but it's overridden by the condition on line 932 if the customer group is flagged." No fluff. It pointed to the exact lines and called out the bad practices without me asking. It got to the point.
Verdict? For explaining real, messy legacy code, Cline's chat passed. Copilot Chat failed. It's like the difference between a consultant who's actually written code and one who's just read the manual.
CRM is a necessary evil
I'm a platform engineer at a 350-person fintech, managing the CI/CD and dev tooling for about 200 microservices and a couple of monolithic legacy apps (Java, .NET, Go) in prod, so I live in this exact "decipher the ruins" space daily.
My side-by-side comparison, focusing purely on the "code archaeologist" use case:
1. **Context Window & File Handling**: Cline's explicit project-aware chat (it reads your entire opened file list and structure) consistently beats Copilot Chat's more implicit, single-file focus for sprawling legacy code. With Copilot, I've had to manually open and paste relevant sections into the prompt to get a coherent answer on a 2k-line file. Cline simply needs the files opened in the editor. This is the difference between a 2-minute task and a 10-minute one.
2. **Response Tone & Directness**: Copilot Chat is optimized to be helpful and safe, which often translates to vagueness on bad code. Cline is trained to be critically direct. As you saw, Copilot will describe the "what" (a method named `calculate` performs calculation), while Cline will state the "what and why it's wrong" (this method violates SRP, contains a magic number on line X, and has a potential NPE on line Y). For legacy refactors, you need the bluntness.
3. **Integration & Workflow Cost**: Copilot Chat is bundled if you're already paying for GitHub Copilot Business ($19/user/month). Cline is a separate $20/month subscription. The hidden cost is setup: Cline requires you to explicitly open the pertinent files in your editor for context, while Copilot tries to infer context from your current file. Copilot's tighter GH Issues/Actions integration is irrelevant for this specific task.
4. **Where It Breaks**: Copilot Chat becomes nearly useless on a single massive file unless you meticulously craft a prompt that includes specific line ranges. It also can't reason across multiple related files (e.g., a parent class and three subclasses) without you doing the legwork. Cline falls apart if you don't strategically open the right set of files first; its context is only what's in your editor tabs, not the whole codebase.
For the specific job of untangling horrific legacy logic, I'd install Cline every time. It's built for that exact "talk me through this mess" moment. The choice flips if your need is broader than deep-dive explanations - if you need AI baked into PR reviews, CI, and general day-to-day code suggestions across a whole org, Copilot's ecosystem is the smarter buy. To make the call clean, tell us if this is a one-time legacy cleanup project or if you need an all-purpose AI dev tool.
pipeline all the things