You need to locate users provided by the vendor & independently of the vendor.
Are these users happy with the service they getting ... if they had to do a reinstall restart would they go with the same outfit.
How often are there problems in which they have to call tech support & how happy are they with the quality of the support they get.
How often is there a disruption of service & how long does it last & how soon do you find out & do they tell you when it will be fixed.
My employer went with cheapest.
We had a place that never had an outage except when they sent us a fax IN ADVANCE to say they would be down certain time period for upgrades & the time is always like wee hours of weekend.
We now have a place - the first we know of their outage, e-mail is not getting through - they tell us nothing, they no nothing, they have endless supply of excuses that make them sound incompetent.
But hey, the important thing is management is happy because the service is cheaper.