NRT or HND?
 

Flights from Seoul are close-enough in price between NRT and HND.
I'll be flying either Asiana or ANA, to use *G status.

Seems like you would fly to HND if you want a shorter commute, and don't care about the airport experience (no shopping, no restaurants, crappy lounges).

Is the extra time to get to NRT worth it, or is HND a no-brainer?

Unless you have a meeting in, say, Ueno, HND is a better bet.

You mean NRT? HND is far superior in every measure, including the lounges. Besides, if you're arriving, why would you care about any of that?

Fly ANA to HND if you can.

To enjoy better lounge, shopping, dining experience and the convenience of HND, look for ICN-HND flight. IIRC, OZ has one.

Ah ... the convenience of ICN...

Quality of lounges depends on your airline.

Another plus for the HND flights is that many (most?) of them operate to/from GMP instead of ICN. Unless one needs to connect in NRT or ICN, HND and GMP are the more convenient airports both in Tokyo and Seoul.

I would not consider the airport "experience" as my goal would be to spend as little time as possible at the airport before departure or upon arrival.

HND is actually in Tokyo, as opposed to NRT, which is 60km (40 miles) out.

I was living in Tokyo when NRT opened, and everyone complained about it, especially since there were no trains that went all the way (and wouldn't be for a couple of years), and the terminal where the direct bus left from was in an inconvenient location.

HND is a brief monorail ride from the Yamanote commuter train line that circles the central city.

HND, always HND: NRT has no advantage ever that I can see

Well, except for the fact that many international flights arrive at HND at very inconvenient times. From west coast US, I generally prefer NRT to allow arrival in mid-afternoon, which means I can connect by rail to points other than Tokyo.

Not an issue when flying to/from Korea...

Depending on mode of travel and time of day, HND will save you about 35 minutes each way over NRT. Also HND flights usually go to GMP not INC which will save you time in Seoul as well. Not much difference in the airport experience between NRT and HND. I usually pick flight in/out of Tokyo depending on schedule rather than airport.

Was just in HND. Both the domestic terminal (with the Excel hotel) and the international terminal are stunning.

Most of the fun is landside, not airside. But the airside (oneworld) lounge was great, too.

HND in a landslide no reason to head out to NRT unless you have to.
Cheers
Howie