OG Kush: Difficult to grow, may yield like shit (the 'abusive' cut does for me), smells amazing, high is AWESOME, only available as clones.
Hindu Kush: Easy as pie to grow, yields more than respectably, smell is spicy and pleasant, high is nice and balanced, available as seeds, breeds true, outstanding anti-nausea properties.
Master Kush: I've had plants of this line but never flowered any. No complaints.