Thanks for all your responses - really helpful.
At the moment I've actually got no experience in either the C206 or C207. From what I'm hearing, the 206 is the main tourist carrier out in Botswana as opposed to the 207. Unfortunately I only have access to a 207 here in NZ (without having to trek all the way up to Taupo and do it).
So I guess the question remains really of whether or not doing the type rating in a 207 will be close enough operationally to be able to handle the 206 without too much effort or conversion required (even if it means that the ratings aren't interchangeable).