Unlocked or locked iPhone - which is better?

I'm looking into buying an iPhone 4s. I don't want a contract (don't send that many texts/use mainly Wi-Fi/etc), and you can find these products far cheaper on eBay than in phone shops.

However, i'm unsure as to which is the best buy: one that is already assigned to a network, or one that is 'unlocked'?

Does anyone know the pros and cons to either of them?

Also, what happens if i buy an unlocked iPhone? Where do i buy a sim card from? How much do sim cards cost? Once i buy once, do i just insert it, or do i have to register with the netwrok? How easy/difficult a process is it?

Any advice or information would be much appreciated.

Unlock is better. You can use it anywhere worldwide. Just grab sim from any network provider an you should be set up ready in 24hours. Follow steps as given in sim booklet

Unlocked! You do not have to worry about provider.

http://www.amazon.co.uk/...n.co.uk/s/" class='ext_link'>http://www.amazon.co.uk/...n.co.uk/s/

http://www.amazon.co.uk/s/

Locked
You can unlock it through a few random phone shops…
It is also of lesser price

Unlocked is better and works out cheaper. Mine costs less than £10 a month rolling sim on t-mobile. I'm like you you send very few text or make calls but use data.