There are performance issues with the UT engine, one of them is blocking of graphics chip at lower main cpu speeds. See:
http://www20.tomshardware.com/graphic/2000...3dbench-02.html
The sound in GR rocked! From the sounds you could EXACTLY get the direction of enemy fire. And the sound quality was like in no other game I have seen.
In Raven Shield(which was built on the UT engine), you can not even tell left from right in most cases. Remember that sounds are also part of a graphics engine, and I am very disappointed with the sound in Raven Shield.
"Netcode". It was good in GR. I am not sure if it depends on the graphics engine, but I strongly believe so. In Raven shield the netcode is a joke.
But most important are the developers. If the master minds from GR can take care of GR2 I do not doubt that the game will be the best MP game ever made.
Just my 5 cents.
May the infinite uncertainty power be with us!