I am not sure if there are any benchmark websites but I feel that Broadcom's Videocore technology is way behind most of the high end smartphone GPU competition, such as Mali, Adreno, PowerVR, etc.
https://www.broadcom.com/products/broadband/set-top-box
I guess they are just reducing their efforts as set top boxes are phased out in favor of smart TVs or Android TV and similar.
Other boards beat the Raspberry Pi in mainline kernel support, USB & Ethernet I/O & price years ago, but there is a significant ecosystem that the Foundation seeks to support, and the best way they know how to do so is with the tools they are intimately familiar with.
You sound knowledgeable, so I'll ask: if you don't care about the RPi ecosystem (or IoT use-cases at all, really), what's the optimum SBC across all those axes currently? Like, what board would you choose to base a cheap one-off HTPC+NAS on?
For a NAS, nearly all of the OrangePis feature USB ports & ethernet that are directly wired to the SOC, so you aren't I/O limited like older Raspberry Pi's. That being said, the Allwinner H3 doesn't support 10 bit Hevc/H.265 acceleration, so you might want to go with a board based on a newer chip for a HTPC. Take a peek at LibreELEC, they have a decent HTPC distro for many SBCs.
v3d:
- v3d v4.2 support
However, Mali changes might help RPi5 whenever it is released in 2-3 years. There's a good chance RPi4 is the end of the line for VideoCore chips. Mali is a logical replacement for it, especially considering recent open source driver improvements.