It does depend a bit on your accuracy requirements and the way your servers are keeping time and interpreting the NTP data. A full NTP implementation aiming to keep accurate time is a surprisingly scientific thing. There are simplified implementations which basically drop most of the internal processing and in-between-timeskew correction and "just sync to the time they are told" - this is called S(implified)NTP.
If you have full-fledged NTP implementations, it mostly would not matter which servers you sync to - as long as you can trust most of them to have accurate time, the algorithms will even out skew and latency issues so the clock deviation will be within the range of a few milliseconds.
If you just have SNTP and want "same time", you are probably best advised by running own NTP server(s) and sync your other datacentre machines with them. Even SNTP implementations should measure the network round-trip-time and take it into consideration before setting the clock, so unless you have vastly varying latencies on your links or really bad clocks in your hardware, things should be within the milliseconds range as well.