Top speed limited may be a result of gearing changes, or artificial limit due to the low resistance tyres. As the 0-60 is unchanged, maybe the gearing is the same and it's just got a reduced top speed as a tyre safety thing. Then again, towing weights are less, so maybe that means they do dial back the top-end power on the engine.
The factory tyre choice is limited to 17 or 18 only, which may or may not be an issue.
Suspension is sports-only to make it sit lower to ground, which increases fuel efficiency and reduces emissions (apparently)
Obviously as the emissions are a tiny bit lower in their test scenarios, then as a result the BIK rate is a whole 1% less (21% vs 22%). Of course, you may or may not believe these figures (I don't), as the reviews from launch in 2015, compared with those from today, the various brochure versions and the current web site all show different emissions values for each model...it seems they just make it up as they go along...
According to my (probably incorrect) Audi spec sheet the insurance group is one higher for the Ultra (27E rather than 26E) although no idea why that would be.
Personally I would say if you can live with the 22% BIK then just get the normal model and spec any ECO features you feel the need for.
