In benchmarks, the IPhone 14 Pro scores higher than a Steam Deck. Needless to say that yes, an iPhone 15 Pro also offers higher performance.

Now utilising that performance in games is another matter entirely. So the deck still wins in real world gaming loads in the few titles you can compare between the two.

See the link for a short comparison by Digital Foundry in Resident Evil 8: https://youtu.be/lseDQie5oRU?si=PX6D4xi8jQlGpZml