My 2c, buy RPi’s because what makes them so great is the availability of drivers and information. You will end up paying with your time if you try to save some money up front. I had several OPi, one randomly started throwing errors. After several reinstalls with various sd card, the information I could find was that the SoC itself was causing the errors. Also getting any hardware to work with it is just a major pain, driver support is severely lacking. Support for the Linux versions is community driven, so you’re dependent on Armbian maintainers. If you have a very new or an older board, you’re probably out of luck when you want to do anything outside of Linux. Example, I could not get a camera and BT module working. I later bought a RPi4 and had the same hardware working within hours.