I would recommend classic.
Classic, almost all PvE is within your realm, so you will not get killed. Only the other two realms can kill you, and that is only in specific areas, not where most PvE is. The simple fact is that if you choose the Co-op server, you will miss out on so much game play. It is like playing 10% of the real game. Sure, you may not like RvR much, but wouldn't you at least want to participate in a siege war against humans at some point?
mordred, i would definitely not recommend, that is teh PvP server and you can get killed by anyone almost anywhere, and you can bet you will.
ToA (regular) servers offer even more game content than classic, but if you are starting new, that is more of a disadvantage to you the first year or so as you will have more than enough to learn on classic. Classic is also the one cluster where you will find other new people to the game. Sure, one might stroll in every week on a regular server, but good luck meeting up with them.