The fact of being able to fly and open and close the doors in flight versus, having to remove doors is a big one if you are going the be taking photos. If you see a good shot or you are getting hot simply pop the door open and take the pic. As far as I am aware only the Bushbaby and the Skyranger with the halfdoor option can do this. The others would require the complete removal of the doors while on the ground.
Next if side by side you are going to need comfort and space, the wide body Bushbaby (Explorer) is just the thing. You would also need accessable luggage areas to pack camping gear and luggage.
When if comes to price the Foxbat is way out of your range, at R420K with a long waiting list. However this is an exquisite plane, very comfortable and super fast. Can't fly with open doors though.
The Cubby is a pain because only the RHS door can be opened and I very much doubt if this can be done in flight. But Tandems are more comfy for two big folks, you don't rub shoulders.
My choices would be
Bush Baby Explorer
Cheetah XL
Skyranger
I think the Savanah is a good plane, great value, full metal but I think the large dash will get in the way of some good shots.
Oh and finally, with no disrespect to Agent, but the Bantam is just downright ugly
