It's sort of hard for anyone to tell you what to get, because we don't know anything about his diving or wants/needs. Has he been hinting for something? What has he said? Can you tell us anything about where he dives, how many dives he's done, anything else?
Before picking out a specific model, you really need to answer the question you didn't know you asked - "dive watch or computer?" There's a big difference between a dive watch that is mostly a waterproof watch with perhaps some diving features like depth and bottom time, and one that is a real dive computer that tracks decompression status. And if the concern is getting something functional for him it can't be picked out on looks first. (Unless that's the most important function you're looking for.
) I'd say on average, the more features a dive watch/computer has, the less nice it will look.
What is making you look at the Citizen watches? (I'm not sure the Promaster is an actual dive computer either, it appears to have logging and be able to upload logs to your computer but those "computer features" don't make it a dive computer. It appears the NX is an actual dive computer. So you've actually listed 3 very different beasts.) There are many brands and models of dive computers out there. Some are watch style models and some are larger though still commonly worn on the wrist. They're not mainstream brands you've heard of like Citizen but well known to most divers. There are some tradeoffs between the watch style and the bigger models. The watch size can be harder to read, as there's alot of information to fit on the screen. And they tend to cost much more than the larger models for the same features. You can generally buy a nice regular watch and a good dedicated dive computer for less money total than a fancy watch style dive computer and they'll probably each be better at what they do.
So what I'm kind of thinking is, while a shiny "dive watch" may seem like the nicest thing to wrap up as a gift and alot more fun than a gift certificate, and even better if it has "computer features", it might not be what he really wants or needs. As a diver if he doesn't have a dive computer and wants one - well while I'm sure he will always appreciate a nice watch from you, it may not be what he really wants or needs for diving.
