I apologize for responding to a post that I think is just being a contrary , I've never bothered taking the time before but today it just got to me .
From your post you are leaning towards going with the Furutech GTX-D NCF that cost $280 without a cover . while I am using Audioquest NGR Edison ( now $80 less than Furutech ) it comes with the outlet cover , it was also on sale for $135 . I would have gone with Cardas ( about 5 years ago ) but then they were using what looks like a Hubble made outlet whereas now they look like they are using an Audioquest made which costs $150 without a cover . I think that all 3 would be equivalent .
As for Medical Grade or HG they are just very heavy duty for being able to handle constant plugging and unplugging and also after taking one apart the 15amp is the same internally as the 20amp !