I don't think the actual server really matters other than if its in Euro or US, much like if you do the "-image" line in the shortcut to GW2 to download all the game files (where you go into the properties and add -image after .exe with a space) you can type in " -diag" and it will give you a text document that has a bunch of info which includes a traceroute to their servers, one listed in Dallas Texas(18.104.22.168) and the other in Frankfurt Germany(22.214.171.124), and gives you the final IP address of the server where when I ping them from Pittsburgh PA (East coast US) I get avg values of 54 and 112 ms respectively
and I say those cities, b/c in the trace route (where you see the IP address of each place you have to connect through to get to the server) the last couple hops (places) have those cities listed as names, but there are a couple more hops afterwards that could take it somewhere else. B/c I've read that ncsoft/arena has a server facility in Austin TX, not sure about in EU, so it might just be travelling through dallas as a main HUB for the Texas area. Additionally, these may or may not be the actual game servers; but the authentications ones. Although, the diagnostic test should connect to the playable servers
but regardless they will/should be in the same location as the other servers.
But my point being, the servers are all listed in one location and other than playing with ppl you know it won't matter which one we are in beyond the two locations (both having fine enough connections for me). The only other thing that affects the server is how many ppl will be in that one total and not just us and how good they will be at WvW; which we cannot determine because nor would I try to just based on betas
If we want to change later, we can always save up enough gold as a guild to pay for everyone buying gems and moving at once if need be. The important thing is that we just agree to be in one location so it is easy to play with each other.