I don't think it makes a huge difference either way.
I have an '06, and have shot the '05 (using same paint, Rampage if you must know) and they both shot equally well... I only noticed that the milling on the '05 is a bit different... They even both had about the same consitancy, running about 275 +/- 3.
All in all, I think they are relatively the same, except that the '06 has adjustable trigger spring tension, and the Alien reg instead of the CP (people may see it as a downgrade, but its really a good performer).
I put pictures here: Flickr
...and here (kinda a work in progress): Squarespace