There are advantages to keeping the city close, and far.
Depends on what you're aiming for.
I tell my alliance members this a lot.
The Advantages/Disadvantages of a Close City:
Easy resource/troop transport - very little time required for both.
People who might want to take your city personally will know exactly where it's at, simply by searching you.
A close city is better for simply a resource gaining facility. It doesn't help much at all for any kind of extra attacking base because it's so close to your original city.
The Advantages/Disadvantages of a Far City:
Could take hours to transport troops. Literally.. all... day... long..
Resources still take maybe a max of ten minutes though

More areas to attack, or be closer to
A far city is more for hardcore players, who want to be able to attack others with less time.
A few hints:
People can only attack you five times in 24 hours - so it is very hard for someone, unless they have others helping, to take your city.
It is better to conquer someone else's second city because resource upgrades transfer to the new owner if the city is taken over
Resources/Citizens/Upgrades do not transfer between cities but Money/Coins/Tech Upgrades do transfer.
Also.. the last post replied I'd like to point out Cavalry does cut the transfer time in half, Infantry takes the amount of time shown. But I do believe Catapults
TRIPLE the time.. Can this be confirmed? Or is Fey crazy? ;o