Platforms first. Bedrock is the edition that runs on Xbox, PlayStation, Nintendo Switch, iOS, Android and Windows, with native crossplay between all of them. It is also the one still often called Pocket Edition or MCPE, a leftover from its mobile beginnings. Java stays PC-only, on Windows, macOS and Linux. The two editions share neither network protocol nor world format: a Bedrock server will not accept a Java client, and the reverse is just as true.
Extensions next. Bedrock is extended with add-ons, behavior packs and resource packs, installed from the panel file manager. Java relies on Spigot and Paper plugins and on Forge, NeoForge and Fabric mods, a far larger ecosystem but also a far hungrier one. That is where the real sizing difference lies: Bedrock stays light where a Java modpack routinely asks for 10 to 16 GB of memory for the same number of players.
So the choice comes down to your community. If your players are on console, on mobile, or split between the two, Bedrock is the only edition that brings them together. If they are all on PC and you are after plugins and modpacks, Java is the way. Our Minecraft Java plans cover Paper, Spigot, Forge, NeoForge and Fabric, on the same Paris infrastructure and with the same level of protection.