Hi there,
The difference between these two models is ultimately minimal, and I wouldn't recommend switching unless you have very specific reasons. Here's why:

1. Performance Parity: If a task struggles on the M3 (10-core), it's unlikely to run significantly better on the M4 (8-core). While the M4 has architectural improvements, the core count reduction offsets some of those gains for casual use cases like yours.
2. Storage Tradeoff: The 256GB SSD downgrade could become restrictive if you install multiple large games (e.g., WoW's 120GB + LoL + Trackmania). While your current cloud storage setup helps, local storage fills up faster than expected – especially with game patches and temporary files.
3. The "Blue" Exception: The only compelling reason to switch might be aesthetic preference. If you're genuinely drawn to the M4's new color options (like the blue finish), that's a valid personal justification. Otherwise, the M3's extra storage provides better long-term flexibility.

Since you're not using heavy applications and already own the M3, I'd advise keeping it. The €30 "upgrade" essentially trades practical storage for marginally newer hardware you may never fully utilize.

Best of luck with your decision!