Can any doc tell me what's the best electronic cigarette?

How about none of. them? The reality is that the makers of these products have published NO results of any studies they have done, and because they have not been regulated, they don't have to. We do not know the safety of the oil used as a propellant when inhaled, or the flavorings, additives and preservatives when volatilized and inhaled. There is formaldehyde in the vapor, a carcinogen. So nobody really knows.