iPhone 12 Pro and iPhone 12 Pro Max come with 6GB of RAM, while the lower-end iPhone 12 and iPhone 12 mini still have 4GB of RAM, according to plist files in the Xcode 12.1 beta.
These plist files accurately revealed the RAM of previous generations of iPhones, according to MacRumors.
Geekbench scores for iPhone 12 Pro also confirm 6GB RAM. iPhone 11, iPhone 11 Pro and iPhone 11 Pro Max all have 4GB RAM.
The RAM boost and the faster A14 Bionic chip will improve the performance of iPhone 12 Pro significantly.