Thanks for the comparison view. I'm still considering the Ego and can't quite decide. We have 510s.
Your wife can leave at least one of the batteries at home if she picks up a couple of the 510 XL batteries. They are a full inch longer and nearly twice the life. My wife takes two with her to work on her six-hour shift and usually uses only one of the batteries. Well worth spending a couple bucks more.
Go the eGo Cliff. I started out with the 510, but the limited battery life was a major drawback for me. The eGo batts last well even with some heavy Vaping, and each kit comes with 2. The charge cycle on a batt is about 2 hours. You won't regret it