Core Differences
Java: PC-only, richest mods, best redstone, ¥165. Bedrock: cross-platform (mobile+PC+console+Switch), C++ performance, ¥71, marketplace content. Significant differences in generation, redstone, and combat.
Redstone Differences (Critical!)
Java: deterministic updates, quasi-connectivity, 1-tick pistons. Bedrock: random updates, no QC, variable timing. Most Java redstone machines don't work on Bedrock. Love redstone? Choose Java.
Combat Differences
Java (1.9+): attack cooldown (1.6s full damage), shield block, axe disables shield. Bedrock: no cooldown spam, but rampant PVP cheating. Java PVP community is larger and more competitive.
Final Recommendation
Java: love mods/redstone/PVP, decent PC. Bedrock: cross-platform with friends, max performance. Buy Java and get Bedrock for Windows free.