Just bought the Samsung T5 500GB SSD and ran some speed tests against the PS4 slim HDD. Not scientific by any means but got some some interesting results. See comment below. Btw
Black Friday deal: get a 500GB SSD PS4 hard drive for almost half-price, today only | Eurogamer.net
Amazon.com: SAMSUNG T5 Portable SSD 500GB - Up to 540MB/s - USB 3.1 External Solid State Drive, Blue (MU-PA500B/AM) : Electronics
PSA: If you are playing on current-gen consoles, installing the game on an external SSD (instead of the internal HDD) can massively improve texture loading and pop-in! : r/cyberpunkgame
PS4-Geschwindigkeits-Boost mit SSD-Festplatte - G-Zockt.DE