If you're building a dedicated local AI rig and your models fit within 32GB, the RTX 5090 is the no-brainer choice, cheaper, faster in raw compute, and newer architecture. However, the moment you touch 70B+ models, run inference with long context, or want multi-GPU scalability, the RTX 6000 Ada's 48GB VRAM and NVLink become non-negotiable. The 6000 Ada also offers ECC memory, lower power draw, and proven stability for 24/7 workloads, making it the appropriate tool for serious AI builders who prioritize capability over cost.
In short: the RTX 5090 is the best 'gamer-AI' card for tinkering with small-medium models, while the RTX 6000 Ada is the real workhorse for production-level local LLM, diffusion, and research workloads. Nvidia's segmentation is intentional, compute-bound users get speed, memory-bound users get capacity, and there is no universal winner. For the primary audience of 'builders running local AI' on this site, we lean towards the 6000 Ada as the safer long-term investment, especially as model sizes continue to balloon.