Wordpress.com is a hosting service for (you guessed it) Wordpress websites.
Wordpress.org is the website for the (open source) Wordpress project, where you can find the installation packages, source code, etc.
Asking for 'hacking rates' between the two is just as asking what is more safe on the road: take a cab to your destination, or build you own car with some supplied parts.
It is just a silly question actually, as the cab driver probably thinks that is none of your business, and building your own car has nothing to do with road safety as you are not driving it yet.
What you probably meant to ask: Is it safer to host my Wordpress website with Wordpress.com, or do my own installation on a server?
This all depends would be my answer: things like functionality play part (if you need exotic plug-ins that might not be supported by wordpress.com), but also technical aspects (your server admin skills), and how you think about security and privacy (threat model, etc.)