Tera just has graphics and combat. When guild wars 2 has both and a actual rich story line for the players to enjoy, with an amazing dynamic event system. offers brand new mechanics and experience to mmos.
But its up to you, if you want combat and good graphics and wanna pay monthly, go for tera. But if you wanna experience all of that, no monthly fees, with a story line and a PvE environment that is built for the players and is revolved around the person that is playing the game, go for Gw2. Basically if you want a fresh new mmo, not the same old grinding ***. Just some reasons to be interested http://www.youtube.com/watch?v=xBC_ig73aMs(video over a year old)