Node capturing and sieging isn't activated yet.. so pvp happens out in the field usually over grind spots where people level 50 and above are trying to get levels. Most of this pvp is small sided battles with less than 10 people but it's not uncommon for a guild to have multiple groups in one area and for larger battles to break out. This recent patch also introduced a battleground which is great for letting people practice pvp without losing xp.

Numbers definitely make a difference, but levels make more of a difference. Like Brommas mentioned, a higher level person can take out multiple lower levels... and if you are lower level and don't have accuracy stacked you won't even be able to hit the higher level players.