Why does the OP not ask the instructor(s) he will be interning with what their opinion is?
Maybe it depends on whether this will be in a resort environment, where the dives follow a tight daily schedule, or an environment where the dives are less predictable? From what I've seen in resort environments, a DM's dives follow a predictable daily pattern--day after day they do the same dives, the same surface intervals, etc. I could be completely wrong--I am not a DM--but I doubt most DM interns at resorts or similar predictable dive operations are being put in a position where they will be on the hairy edge of NDLs. The DMs who do these dives every day could probably get by without computers at all, though nobody would dispute it's wise to have them to handle the unexpected. Surely the people who are going to be giving the OP instruction can tell the OP what they do to keep themselves safe, and whether they believe choice of computer makes much difference. I have seen DMs with nothing but a Timex Ironman on their wrists. Maybe not especially wise, but for the daily grind maybe that plus some rules of thumb equals enough to keep most of them from getting bent.
What I am saying is that maybe the OP or others who have made specific recommendations are over-thinking it. Any computer ought to work fine for this purpose. After all, "any computer" is what the people the DM leads are using. I suspect the OP's fellow interns will show up with "any computer," too. So I would suggest using the same criteria to select a computer as anyone else.
Maybe it depends on whether this will be in a resort environment, where the dives follow a tight daily schedule, or an environment where the dives are less predictable? From what I've seen in resort environments, a DM's dives follow a predictable daily pattern--day after day they do the same dives, the same surface intervals, etc. I could be completely wrong--I am not a DM--but I doubt most DM interns at resorts or similar predictable dive operations are being put in a position where they will be on the hairy edge of NDLs. The DMs who do these dives every day could probably get by without computers at all, though nobody would dispute it's wise to have them to handle the unexpected. Surely the people who are going to be giving the OP instruction can tell the OP what they do to keep themselves safe, and whether they believe choice of computer makes much difference. I have seen DMs with nothing but a Timex Ironman on their wrists. Maybe not especially wise, but for the daily grind maybe that plus some rules of thumb equals enough to keep most of them from getting bent.
What I am saying is that maybe the OP or others who have made specific recommendations are over-thinking it. Any computer ought to work fine for this purpose. After all, "any computer" is what the people the DM leads are using. I suspect the OP's fellow interns will show up with "any computer," too. So I would suggest using the same criteria to select a computer as anyone else.