I have found that external meetings have been more rewarding than internal meetings regarding potential new customers, what are your opinions on this?

Depends what is agenda of your meeting, but some functions are more external focused. For example, it's better for sales people to try their sales pitches on external clients, rather then practicing it internally. 

Depends on the human nature of the customer  & Ethics background.

from my point of view I agree 60% with you.