Need advice on hardware purchasing decision: RTX 5090 vs. M5 Max 128GB for agentic software development

RTX 5090 vs M5 Max 128GB for local LLM inference is a real tradeoff: 5090 delivers roughly 3x higher token throughput on Qwen3-27B but caps at 32GB VRAM, forcing aggressive quantization like Q4, while M5 Max 128GB unified memory enables Q8 or full BF16 at larger context windows. For agentic coding workflows where latency compounds across multi-step tool calls, the 5090s speed advantage likely dominates. Neither is objectively correct without knowing your typical context length and whether you chain multiple model calls per task.