G'day,
naturally the GP Forum might bring some biased respones; nonetheless, i do have a very soft spot for IWC (and happen to like the new "Top Gun" model!).
To me, both pieces in question are very different.
The GP scores in terms of the manufacture-made movement vs. the IWC-tuned Valjoux base; the case reflects the different functionality, while i tremendously appreciate the efforts that go into the "1.000m". These are much more than apparent, which we´ll see very soon in details.
The style is a matter of taste; the "Sea Hawk Pro" model in Titanium is a lot higher, which makes the steel "1.000m" more wearable while not loosing the substantial impression on the wrist.
On the other hand, a chronograph is an interesting function and the "Cousteau" tie makes for an interesting story, while IWC´s "GST"-range bracelet is among the most comfortable and easy-to-use bracelets around.
So both do have their merits; personally i´d prefer the "1.000m" for the rarity, the more individual and unusual design and the fact it´s a manufacture-made movement (and complication).
Still i´d recommend to try both; neither is a small watch and the "wrist feel" probably is the best indication which will speak more to you.
This may require a little patience, in that the "1.000m" just is under delivery in a small number of units and not every dealer will receive one these days.
Cheers,
Peter