I would never go for an iPhone at any price. I just don't see the benefit. The S7 is water proof (1.5 meters for 30 minutes), has a microSD card slot, a OLED QHD screen, fast charging (1 hour 40 minutes to go from 15% to full) and fast wireless charging. The iPhone has none of that plus Pokémon GO is a big drain on the battery.
That said it is ultimately up to you as it will be what you prefer. The iPhone is more simplistic and easier to use but to me it is just meh hardware wise.