Decide where is the main target audience of your server. If it is in Europe, run some traceroutes and pings and compare the results.
You can also ask for a download file if that is more of a concern. Generally, unless your usage is either ping sensitive (such as game hosting) or download intensive (download server), most datacenters should do the job well.
Also as a general rule of thumb, a data center nearer to the destination should perform better. That is why if you do have a rather niche target area or market, this would come into play.
Sprintserve Thanks for your rep. i am new at WHT but i read a lot of threads (WHT scanner).
The server is a webserver (serving small traffic companies) all the money from hosting invested to dedicated hosting in order to learn.
Once again i' d like to thank you 4rep.