First of all, I've looked over the program comparison chart that is linked from this forum. It didn't really answer my question that well, so I thought that I would try asking here.

At the moment, I am living in the US. But, if all goes according to plan, I will be living and working in Japan.

I will be flying UA in a few weeks, and I was wondering whether I should join their program (since they will likely see more of my $$$ in the short term) or NH's program, since they will get more of my money in the long term and I would (hopefully) have enough miles by then to get some free tickets.

Thanks!

I don't have personal experience regarding this but there was a thread in the NH forum (I think) recently which mentioned that for NH discounted tickets, you only get 70% credit, etc. So over time this would add up. On the other hand, if you will mostly be flying NH, you would be able to take advantage of NH specific perks which wouldn't be available to you as a *A gold on NH e.g. upgrades, etc.

How many miles a year do you think you'll be flying?
What class of service will you be using?
Do you have any status with UA now?

No status (or membership whatsoever) with UA at the moment. From the looks of it, short-term I would be flying about 30,000 miles a year with UA. Longterm, with NH, many more due to frequent (at least monthly) trips between the USA and Japan. Maybe over 100k counting domestic stuff and other *A carriers.

Probably mainly economy short-term, unless I could get upgraded. I'm on a student budget.

Thanks for the help!

30,000 does not qualify you any elite or gold status. If any shot, I would suggest you to join Air Canada's Aeroplan, which has the lowest threshold of qualifying for Star Alliance gold status: 35,000. As a Star gold, you can at least use the lounges at any Japanese or US airport.

NH has the best service, while overall all these foreign airlines employ Japanese, so whether you are with UA or AC, you are usually best serviced.

You have to fly many more NH domestic flights (although they may give two points for one mile actually flown).

I stop over NRT once a year to visit my brother who lives in Tokyo. Checked out all the lounges, flown UA, AC, NH, SQ, in and out NRT, and basically if you are on budget and have to fly economy class, acquiring a *gold status is the best perk you can reach. In this case, AC's Aeroplan is a good choice.

Biggest problem with ANA's scheme is the points only last 3 years. Unless you can earn quickly, (and 30,000 for the first year is not quick) then just as you are ready to start burning them - they will expire.

Another advantage of getting non-US Star Gold, is that you can go into the lounge on domestic flights, when not connecting to an International flight.