Here is a review of the HumminGuru that does some comparison with the Degritter. Not sure that some of his tests are valid but there is some interesting info buried in the review about how each works. He's a big fan of the Degritter, so his conclusions aren't necessarily surprising.
Despite that (and other similar reviews that I have read), I'm leaning towards the HG. $3,000 dollars for a cleaner is just a LOT of money compared to the other components in my system and/or my total record spend. Also, I typically purchase new vinyl or VG+ or better used discs, so I'm not asking my cleaner to perform miracles from old garage records. The HG should still be a step up from the Groovewasher system that I use now and I can always pass my HG down to one of my kids (2 are into records) down the line and upgrade to something like the Degritter.