I always use the Magneto utility. It just seems OP'd. But I haven't really found an offensive / defensive combo that I like for Adrian yet.
I'd be open minded to switching the Mag utility if there were a better combo of boosts!
I found that Colossus/Juggernaut defense is the best no matter what character/power set.
For offense, any of the X-Genes that cause a stun effect on enemies is great - Surge/Cyclops/Magneto.
Sorry I don't have specific info on the shadow power set, I've mostly played the other 2.
I'm glad you asked, as I'm at the moment playing the ever-living hell out of Shadow Matter (Aimi in this case)
Shadow Matter is about speed.
Speed speed speed.
So slap Psylocke's defense X-Gene on.
Being able to phase through enemies to escape is extremely useful and will save your butt big time.
For offense, you've got flexibility.... Wolverine's is just raw damage.... very useful.
If you're using Shadow Grasp or Dark Vapor (Aura powers) You might invest in Cyclops or Psylocke's Offensive Genes as they can affeect Auras... (note Psylocke's probably isn't one to use on Dark Vapor)
If you don't have Life Steal... things get a bit trickier... Wolverine's defense Gene might be useful. The problem with Juggernaut's is that your dodge becomes a push.... making it harder to escape.
Finally, if you use Infinity Rift (broken) - Surge and Iceman's X-Genes greatly enhance that, on top of the crowd control damage enhancement they give normally.
Finally, if you just want to resort to normal dodging... Emma Frost's X-Gene gives extemely useful defensive buffs.
Personally, I go with Surge Offensive, Psylocke Defensive, and Magneto Utility
Jill Valentine > You
Ok, changing my opinion....
Finally got Magneto's Offense X-Gene on my Shadow Matter character....
It's only 1 node but it gives a high level of battlefield control.
I'm thinking that might be the Offensive Gene of choice.
Jill Valentine > You
I like the Northstar Offensive, actually. It seems to stun enemies on a pretty regular basis. I also use the Avalanche Defensive and Northstar Utility, though that last one is because flying is fun.