If you want to play Minecraft with friends who own other systems, your best bet is to buy Minecraft: Bedrock Edition. The Bedrock version has cross-play, meaning you can play with a friend even if you're on PC and they're on a Nintendo Switch, for example. The Java version only allows you to play with other Java users.

Should you buy Minecraft Java or Windows 10?

Objectively speaking, the quality of Java mode is higher than the standard of Minecraft Windows 10 mods. After all, the original edition of Windows 10 version was designed for mobile devices, so the modified scene will always be catching up.

Should I buy Minecraft Java or bedrock?

Due to the Bedrock Edition Engine being designed to be played on PC, mobile, and console, it's generally a more forgiving platform and performs much better on lower-end hardware than Java Edition does.