In my opinion: Gateway offers little compared to current CFWs (you can run .3ds files from the GW red cart, which if you need the simplicity, is good, but that's it). You can actually do more with CFWs:
- You can run GBA games on AGB_FIRM for full-speed emulation.
- You can run SaveDataFiler with retail carts (can't do this with Gateway) to backup and manage your saves (there are open source homebrew versions of SaveDataFiler, but they're not quite as good yet).
- You can safely update your system firmware via rxTools devmode to 9.0-9.2 (or use Cooking Mama 5 EUR; your flag indicates the UK, so I assume you have a Euro 3DS), allowing you to cold-boot CFW right from when you hit the power button.
Basically, I would recommend updating your system to somewhere between 9.0 to 9.2 (no higher!), and just autoboot right into a CFW.