Did you not read the spec sheet?
Snapdragon 680:
CPU - Quad Core Cortex-A73 2.4Ghz + Quad Core Cortex A53 1.8Ghz
RAM - 4GB Dual Channel LPDDR4
GPU - Qualcomm Adreno 610 - 312 GFLOPs FP32
Tegra 4:
CPU - Quad Core Cortex-A15 1.9Ghz
RAM - 2GB DDR3L
GPU - Tegra 4 - 74.8 GLOPs FP32
We even have benchmarks for both:
Benchmarks, information, and specifications for the Qualcomm Snapdragon 680 4G
www.notebookcheck.net
Benchmarks, informatie en specificaties voor de NVIDIA Tegra 4 laptop processor (CPU).
www.notebookcheck.nl
As you can clearly see, the 680 is more then twice as fast (Geekbench 4.4). Which makes sense, it's about 8 years newer.
And no, the Raspberry Pi 4B is not more powerful, it's a older Cortex-A72 quad core that is clocked lower with a vastly weaker GPU.
I'm not speculating and there is nothing to add up, we literally have the specifications of both devices. There is no guessing what the Portal is capable of we know exactly what it is using, its been used in dozens of smartphones and tablets already.