Quote from PsyI remember using UnrealED for the first time after being with Hammer for so many years and I was amazed. It really is a great editor and engine which topples Source in every imaginable way.
I wouldn't go that far. Its certainly better than source in many regards but definitely not all. Not to mention Source's 2004 release as opposed to Unreal 3's cameo in 2006. (I believe) So it is a much older engine, and so far is going to hold up ages longer than Unreal.