Simplenote lives up to its name. It's as simple as notes apps get: type something, it saves, it syncs to all your devices, and it searches instantly across everything you've written. Made by Automattic — the same company behind WordPress.com and Tumblr — it's completely free, fast, and available on every platform imaginable. For pure note-taking speed and cross-device access, it's difficult to beat.
Snoq is also simple to use, but simple in a different direction. There's no sync because there's nothing to sync to. You write a note, it's encrypted with AES-256 before it touches disk, and it stays on your machine. No account, no Automattic servers, no cloud infrastructure of any kind. The simplicity here is about removing every piece of the system that could be a privacy risk.
Both apps are genuinely easy to use from the first minute. The difference between them is entirely about what happens to your notes after you write them.