I use the both internal & external I find on both that depth of field is something you have to use to & it can take a little while to get the
Hang of it. I would say that the external are more user friendly as has been said you can remove them under water, I think I got mine from dryron which push into the front of my SeaCam port. When I use my 12/24 wide angle Nikon I use a Lens diopter with a small
Dome port which sharpens the edges a great deal.
Hi I go to Malta quite regular I use a cool bag to transport my housing, I place it the bag during surface intervals, to keep the sun off it more than any thing else. I only make sure the port is clean before the second dive, only rinsing it back at the dive centre. i have never had any problems, i think that all housings what ever the make are more robust than we all think they are. I think build up of Sea salt on the port glass is more important between dives. Also Tim makes a great point,their is no point not take your camera. Only my two cents worth. Andy