At publishing time, Raspberry Pi 4 boards were widely in stock at all the U.S. and UK outlets we checked. However, given that the Pi 5 models with 4GB and 8GB of RAM cost only $5 more than their Pi 4 equivalents, most individual makers would be right to prefer the new model.

However, companies that are using Pi 4 either within products or for enterprise use cases may want to buy more of the older board, because the Pi 5 isn't a drop-in replacement. It requires new chassis, a higher-wattage power supply and (in most use cases) an active cooler.