What is the benefit of buying the iPhone 5 sim only?

What's the advantages and disadvantages of buying the iPhone 5 sim only ? Everyone says it cheaper but I need at least 700 mins and 1GB internet so I think it works out more expensive for me . Also you lose out on the upgrade if you go sim only right ? As in the loyalty discounts..

Applejuiced said:

Depends on the country and carrier you're talking about.
Not everywhere is the same.

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I'm in the UK . Not sure which network, I do know o2 and vodafone do not have 4G Lte as of yet