My experience for what it is worth... Buy (with in reason) the best you can afford. I was in a similar position to you a while ago, so many options I was just fed up of thinking about the pros and cons of each choice. I ended up making the decision between the top pen at the time (the exact model I can't remember now) and the what was new OMD EM1. I already had a pen camera with only housing so ended up going for the cheaper upgrade with the new pen.
It wasn't long before I ended up cutting my losses and opting the the far better OMD and Nauticam housing. To put it bluntly the controllability you get is far better (for underwater use is a major factor), the build cost is far better and robust. So if it means saving a bit longer I would do that or look for a used setup.
Ask around if anyone is using the setups your thinking about and compare the two. If your in the South West I am always out diving with my EM1.