From my location (Hong Kong) ping to US west (LA and SJ) and east (North Carolina), and Netherlands in EU, in the evening rush hour.

Here are the results.

ping to LA:

 10 packets transmitted, 10 packets received, 0.0% packet loss
 round-trip min/avg/max/stddev = 217.194/262.095/305.338/32.124 ms

ping to SJ:

 10 packets transmitted, 10 packets received, 0.0% packet loss
 round-trip min/avg/max/stddev = 224.676/280.207/325.828/33.598 ms

ping to North Carolina:

 10 packets transmitted, 10 packets received, 0.0% packet loss
 round-trip min/avg/max/stddev = 314.719/362.563/570.972/74.475 ms

ping to Netherlands:

 10 packets transmitted, 10 packets received, 0.0% packet loss
 round-trip min/avg/max/stddev = 363.381/459.670/616.102/85.413 ms

As you see the average time of RTT, US west is 100s faster than US east, and US east is almost 100s faster than NL.

So from Hong Kong I should prefer the IDC location as: US west > US east > EU.