I don't think there will be a huge real world difference between the WWL-1 and the WWL-C when it comes to image quality. I have the WWL-1 and love it. It can be taken off underwater, but the size of it becomes a real pain if its taken off unless your buddy is willing to hold it for you.
I think it all depends on how you want to dive. If you want to have a larger choice of subjects, and are willing and able to spend plenty of time with your subject, moving strobes around, maybe rebalancing the rig it you need to go vertical, then the MWL is your answer.
If you prefer to dedicate a dive to one particular style, then I think you'll find one of the WWL variants better.
Personally - and this isn't right for everyone - I prefer to go into the water with a particular mindset, be it macro or wide angle. Yes, I may miss some opportunities, but I'm usually set up pretty good from the start and I find I'm more tuned into looking for a particular shot if my lens choice is a little limited.
Mike