I’ve got a problem where I dont know what to choose. I have a system which has 768MB of RAM and a CPU which only has 1 core. Im at the MySQL configuration size. Which option am I supposed to choose? The one with 512MB? Or should I go lower. This system will also run teamspeak and other stuff.
You should choose based on your expected use of MySQL, 768MB sounds like an Azure VM? 
Personally, I choose the smallest. I don’t see any performance issues no matter how hard the database is getting hit. But I don’t have millions of visitors on any site (I would say I only have a few hundred mysql hits per-day perhaps).
It all depends on your expected load.
-Dustin