Decisions:NEED HELP!

On a Semi-related note to this assignment, I've been having a lot of trouble deciding which Game engine would be best to use for this Massive Multiplayer Online game and any feedback would be greatly appreciated. 

the choices i'm currently tied between at the moment are 

Unity

Unity (also called Unity3D) is a cross-platform game engine with a built-in IDE developed by Unity Technologies. It is used to develop video games for web plugins, desktop platforms, consoles and mobile devices, and is utilized by over one million developers. Unity is primarily used to create mobile and web games, but can also deploy games to consoles or the PC. The game engine was developed in C/C++, and is able to support code written in C# or javascript. It grew from an OS X supported game development tool in 2005 to the multi-platform game engine that it is today.

(From Wikipedia)

Unreal Development Kit (UDK)

The Unreal Engine is a game engine developed by Epic Games, first illustrated in the 1998 first-person shooter game Unreal. Although primarily developed for first-person shooters, it has been successfully used in a variety of other genres, including stealth, MMORPGs and other RPGs. With its code written in C++, the Unreal Engine features a high degree of portability and is a tool used by many game developers today.

(From Wikipedia)







I've heard a lot of good and bad things about both the engines so i really have no clue what to go with D:


HELP PLEASE!


thanks!