AV-8B hands down, and I finally broke down and got a forum account just to say it.
At the risk of seeming too 'Merika-centric, the AV-8B is the most iconic jump jet in the world and the Night Attack variant offers a lot of outstanding opportunity for an amazing ground-attack aircraft. It wouldn't be the first night fighter in DCS, with the A10C offering enough onboard systems to fill that role just fine, but to me that proves that any extra armament on the GR9 would prove irrelevant when someone can just as easily use the Warthog in an online match. That would make the Harrier a forgettable and irrelevant addition to the DCS line-up, and would be a very poor choice on the part of RAZBAM marketing.
Meanwhile, the AV-8's gun pod and VTOL capabilities (versus the GR7s mostly STOL takeoff) would make for a fun, interesting, and unique edition that people will be sure to purchase instead of just passing over it in favor of other ground-attack or multirole airframes. Bare in mind by the time the Harrier launches the Mirage 2000 will likely take the fore-front as the premier multi role airframe in DCS, making the GR9 irrelevant as a tactical fighter as well. The only future this module seems to have would be by embracing the gun pod, VTOL engagement, and the optics systems that would only be available in the AV-8B package.
With the AV-8B, the Harrier will become an important team player in flights after the introduction of the F14 and F18 while remaining relevant in an online setting. Moreover, the AV8 can use in-game Naval assets that are already available by launching from American aircraft carriers instead of relying on the addition of new British naval assets that rely on the use of a ski-jump to launch fighters.
