I usually call nvidia's SMX a core. Nvidia's warp/hw thread architecture is sure interesting, but one has to remember it's mostly to get around memory bottlenecks. All those contexts need also a lot of gates. GDDR5 has high throughput but has an order of magnitude higher latency.

Ray-tracing doesn't really buy much unless you're doing some specific subset of effects. Rasterization covers 99% of cases with higher efficiency.