All of our UPS systems are located in power distribution room of the building - and wired to Red outlets in the respective rooms. (we have 6 server rooms - supporting 160 servers/SANs/Blade equipment.
Only the Power people know for sure which UPS is taking care of which Server rooms (unless you are good at reading electrical blueprints).
That costs much more - but if you are using an APC or other manufactures of UPS systems - then OK to have it in the same room, you are going to assume that risk. You could propose the larger UPS and the less risk to management and let them make the decision.
If it is powering all 20 servers - it maybe cheaper to go with the centralized and wiring just for the power load it needs, length of up time provided and the multi-function of conditioner/stablizer/UPS systems.
All depends on the size of the UPS and the budget you have to work within..
Hope this helps..