Different ph. Virosol acidic and ubik is alkaline. Useful for their different ph values.

Virosol has a PH of 12.8
UBIK 2000 has a PH of 13.4
I emailed clover in 2013-14 and asked the same question.
Basically the MAIN difference was one if safe to use in food prep areas the other isnt advised but is considered "OK" to use.
When i asked them what i was cleaning they said UBIK 2000 was far better suited.
As for staining. I have had staining 3 times with virosol and never with UBIK 2000