I made a similar post before, (you can do a search for D50 on this forum and see the different opinions...), but at the end I bought the D50, and this is why:
1) The D50 is newer, technical speaking is better than D70 and have the same technical advantage that D70s (except for the control issue)
2) MONEY IS AN ISSUE, and D50 is cheaper, so you save money for the lens, and for a second body.
3) The control issue actually is not an issue if you are not a photographer used to the have the 2 controls (as my self), and this is the excuse of 99% of the photographer who tell you that go for the D70s.
4) Is a really, really good camera.
5) As for the housing, go Ikelite (I assuming money is an issue), so If you going to expend 3000$ on an alloy housing, is a fool decision to go with D50, instead get D200.
6) The main difference between D70s and D50 is not the camera, is the photographer.
So this is my humble newbie opinion, and my two cents on this issue.