Regarding the BBB/BBG, in the last 3-5 years the RPis have gotten significantly faster (RPi3 & 4) and gone 64-bit whereas the BBB & BBG haven't changed much (aside from a bit more eMMC and a very minor CPU bump) since they were launched. These days the 1GHZ 32-bit AM3358 (BBB RevC) is comparatively much slower and with only 512MB RAM, that's a lot less than a stock RPi 4.
Having said that, the BBBs are a great device! They're rock solid and have far better I/O options than the RPi: 4 UARTS, multiple I2C, SPI & CAN buses, EHRPWM, a ton of GPIO, 2x PRU processors, LCD driver, both USB and USB Gadget, oh and of course, the onboard eMMC is great compared to booting from an SD.
I would consider the Black and Green to be competitors too.
https://beagleboard.org/
Would be really interested to get a good analysis of the Raspberry Pi, BB Black, and this new board.