There's really very little overlap.
The 800dv sounds way more unwieldy and nasty.
The Cat sounds really big, and 70s futuristic.
The Cat is much more conventional in terms of layout and editing. No doubt it's capable of way more sound FX than the 800dv. It's way more useful in a studio in regards to CV/Gate and inputs. I look at it like a much heavier sounding Odyssey.
With the 800dv you sort of throw knowledge to the wind and just mess with stuff, and land on strange patches. It doesn't even have an LFO to filter, so you have to really go at it from different angles. I.e. have one layer triggered so it fires the filter ENV, so you sort of have a shapable LFO on that layer, while the other is not triggered. I really couldn't grasp exactly what it was capable of until I finally bought one.
Although not recorded DI, here's a demo of me just messing around with my 800dv.