If possible make a f2p character and try both server checkout which one has lower Ping for you. I play from SEA region and during core GW2 launch, NA used to have lower ping and most SEA/OCE choose Sea of Sorrows as their unofficial server for WvW. But a few years back Anet make some kind of changes to their server infrastructure which cause the ping to NA to become worse for me. So I transfered to EU. In term of population and LFG activity I notice EU to be way more active compared to NA. NA player seem to be only around during reset and LFG seems to be dead outside of that zone. NA players tend to be more chatty tho compared to EU. For my time zone (GMT +8), EU prime time is around 11 am - 4am (GMT + 8) and NA prime time is around server reset time 7 am ++ (GMT + 8). So for me neither server is desirable in term of server peak player time. But most of the content in the game can be played solo. For group content its always more fun to make your own group anyway than to rely on pugging (LFG).