Service Now has an incredibly clunky UI in terms of actually finding what you want, but at least in our JIRA Datacenter vs Service Now (it's under a service now domain, so I assume some sort of cloud setup) setups with several hundred thousand issues in each, Service Now is actually pretty fast in the sense of "You click an action and it does it's intended purpose", where JIRA falls down. It's slow only in the "You need 5 actions to get to the thing you want" sense.