This is the first case I'm aware of since Swift introduced the 804ED about 1990 for a company to market two versions of the same model.
As in the case of the Swifts (not the current 820 vs. 820ED), it would be very unlikely for the HD versions to have no positive effect on the view, and the ease of focus, maybe, but it will be subtle and probably show up as Arthur indicated. I doubt that "WOW, the difference is as clear as the nose on your face..." will be said very often or with much credibility.
Keep in mind that to get these subtle features a considerable investment will be required, which may be dubious if you already enjoy what you have. For example, I recently got a mint standard HR/5 804 Audubon tuned up to perfection. Yes, I can see a difference from the 804ED, but the standard model is fantastic and provides 95% of the view, and if I owned one I wouldn't rush out to buy the other. I have both because I'm a collector — and BTW my whole Swift collection costs less than one Ultravid.
Ed