AI-Assisted Code Completion in Modern IDEs: A Comparative Study

Abstract

AI-assisted code completion has moved from pattern-matching snippets to context-aware suggestions generated by large language models (LLMs) trained on code and natural language. Modern integrated development environments (IDEs) embed these assistants as always-on pair programmers that promise productivity gains, fewer defects, and faster onboarding. Yet teams often struggle to compare tools rigorously across languages, tasks, and governance constraints. This paper presents a structured, simulation-backed comparative study of four representative approaches to completion inside contemporary IDEs: (i) a baseline syntactic engine (traditional Intellisense-style), (ii) a local LLM assistant (runs on developer hardware), (iii) a hybrid LLM assistant (cloud model with on-device/context filters and policy checks), and (iv) a cloud LLM assistant (fully managed, strongest model capacity). We frame the evaluation around research questions on productivity, quality, and risk, define standardized metrics (task success, keystroke savings, time-to-completion, post-run error rate, security-smell rate, and perceived usability), and report results from a controlled simulation fed by empirical distributions observed in typical enterprise tasks (CRUD services, data wrangling, tests, and refactoring micro-tasks).

Descriptive statistics, bootstrap confidence intervals, and one-way ANOVA indicate that LLM-based assistants substantially reduce time-to-completion and increase keystroke savings versus the syntactic baseline. Cloud and hybrid assistants show the largest productivity deltas, while the hybrid approach exhibits the lowest simulated security-smell rate. Local LLMs deliver meaningful gains with improved data-control properties but trail on long-range reasoning and multi-file edits. We discuss implications for tool selection, integration patterns (prompt  templates, test-first workflows, and guardrails), and limits (hallucinations, style drift, and privacy). The study closes with actionable guidance for teams to align assistant choice with repository scale, compliance posture, and developer ergonomics.