Service-Now is too heavy and it takes quite some time to get it implemented. It is a tool where the maturity of the organization needs to be more developed. TOPdesk was the perfect package for our organization as it is easy to implement, cost-efficient and comes along with an excellent support by the TOPdesk staff.
TOPdesk is well suited if you are implementing your first ticketing tool and/or if your organization is less than 2000 users. Also, if your organization has no high ITIL skill level. The TOPdesk team helps a lot to compensate this.