The point is not whether a watch can or could beat a diving computer, but one can take the shortcuts one likes.
The point is more to design a divers watch faithful to its function. This function is something from the past, but watches can still be designed with the eventuality to be used at their best underwater. hence my comments on size, material used, readibility and so on. Or let's call them sport watches.
in terms of marketing, the race is about how deep your diver watch can be rated to. it just create bigger cases, heavier cases and allows to put a nice number for the pressure rating. if mine is rated 1000m and your 500m, mine must be better (unless it is a chrono and then the manufacturer puts in his manual that you should not operate the pushers underwater). I think there are other ways to differenciate but the race to depth is a quick and easy. As the market contains only a very small portion of people who dive with watches ( for fun or old habit), this will bring us even bigger watches, with even deeper rating, more metal thicker sapphire glasses and so on.
coming back to JLC, the pressure test bench they have is rated 400 bars (equivalent to 4000m). I would not be surprised to see in the future a diver watch rated 4000m with an even biger case that 46mm and with lots of metal and sapphire. titanium would be called to rescue if it is not some even lighter material.
the deepest dive ever made by a man in a pressurized chamber was at the depth of 701m (deepest in water was 534m, both by comex in early 1990s). it is safe to say that decades will pass beofre this record is eventually beaten ( as this record was established at a time when men and robots were competing for deep sea offshore oil and gas work, but soon after the record, the robots were privilegded so that no man would be put to these depths and dangers on a regular basis).
size: you mention 44mm for the alarm, but the one with the depth gauge is significantly bigger, so is the chrono. the new ploprof is definitely bigger than the original one. I am sure plenty of people like it this way.
complications:
I think the alarm complication in a diving watch is rather cute and definitely a nice recall of the past of the brand. it is some playful thing that I'd love to hear underwater. It could also be used as more and more dive sites now restrict the time divers can spend underwater in one praticular spot where fauna is abundant, in order to protect the environment and this fauna and not to disturb it too much. It works also great to wake up the diver who could oversleep and be late for work during a normal week. no harm done. especially when the dial remains very readable.
tourbillon is found in all sorts of weird watches, none of which I would consider a diver watch. so are other complications coming in to add function to the detriment of readability. Watch brands develop many things for many different tastes. that;s fine/
I would not want every diver watch to be the same. that would be horribly boring. however, if in a line of diver watch there was one designed with the purpose of diving in mind, that would not be too bad, would it? It becomes harder to find, these days.
the divers watches are useless in the modern times of dive computers: yes ... and no. a good chrono would still be very useful to add 1 min of safety to a safety stop. It seems really hard to achieve and record with modern computers (not impossible, but usually involves a playback of the dat at surface). other complications would also be useful for sure ( I have a couple of suggestions in my bag of tricks
For titanium, t seems that titalyt surface treatment of the titanium surface is well above the pack in terms of hardness. My experience of titanium grade 5 showed me that this metal is very prone to scratches and difficult to polish back. I appreciate all references shared here showing that titanium grade 5 is harder than steel. I can only oppose my little experience, which by no means should be considered as true scientific xeperiment.
Market aspirations:
I feel that a diver watch rated to 500m, with all crowns functional and tested at that depth, clean readable dial would differentiate well from a lot of what's on the market and would sell like hot cookies on sunday morning as well as carry a stronger message from the brand to the clients.
now I can't wait for the day when I will bring one of these nice NS underwater... and something tells me this day is not that far...