A CW has 4 options when it comes to picking a race.

 

 

Human
+2 to any Ability (preferably INT) Versatile Defense: Increase your Defense by 3%.Heroic Effort: You gain an additional Heroic Feat point at levels 10, 15, and 20. The extra 3 points are useful mostly on single target builds as they can spec both Focus Wizardry 3/3 and Learned Spellcaster 5/5.


 

 

 

 

Dragonborn

 

+2 to any 2 Abilities, Int and either Cha or Wis.
+3% increase of your power and Critical. 
Dragonborn was believed so far to gain the 3% only from the main stats which made this choice not a good one. A test I did tho showed that the 3% actually applies to all sources of power and critical including companion bonding gift and legendary bonus as well as DC and Paladin Powersharing. Based on that it brings it very close to what the Human race offers.

 

 

 

 

 

 

 

Tiefling
+2 Charisma and +2 Intelligence.
Bloodhunt: You deal an additional 5% damage to targets below half health.
Infernal Wrath: Whenever you are hit, you have a 10% chance to lower the Power of the attacker by 5% for 5 seconds.

 

 

 

 

 

 

Drow
+2 Dexterity (kinda useless)
+2 Charisma or+2 Wisdom.
Darkfire: You have 5% chance when attacking a foe to apply Darkfire for 4 seconds.
Trance: You recover at campfires twice as quickly.
Essentially a race for Wizard that feels unique. Darkfire is a 5% debuff that can stack up to 4 times (very hard). Suggested only for hardcore debuffers. Select Wisdom and Int and main stats for the AP gain and recharge speed.