There are two lvl 70 starter zones to choose from. All up to the individual player whichever zone they choose to start at in Northrend. Borean Tundra in the West of Northrend continent. Starter area for Horde is Warsong Hold accessible via Zeppelin from Orgrimmar. For Alliance Valiance Keep via Stormwind Harbor.
Howling Fjord zone in the East of Northrend continent. Starter area for Horde is Vengeance Landing via Zeppling just outside Undercity the new one. Alliance starter area at Valgarde via Menethil Harbor.
Which area you choose to start at is entirely up to you the player and what you personally like. There are nice quests in either areas especially the immediate starter landing areas. My opinion wont be real balance here though if you want my best opinion for a overall starter zone Howling Fjord is my better choice for a overall fun, nicer feel, more enjoyable and better looking zone. Just my unbiased and unbalanced opinion. However whichever you choose is up to you. Just hope everyone else goes to Borean Tundra due to easy access from Orgrimmar and Stormwind and clog the starter area up there for good reason. Feel free to give yours.