Mobal is still your best bet even though it's more expensive. If you have an emergency cost won't be the issue. Reliability and convenience will. None of the global SIMs are as reliable and convenient as Mobal.

Depending on how much you will use the phone "occasionally" the added expense of another global SIM may or may not offset the higher airtime of Mobal.

What is so special about O2's roaming agreements that makes it the 'gold standard' when compared to other operators' roaming agreements? What about Vodafone or other multi-nationals like Orange or just large operators like China Mobile, AT&T, and Rogers Wireless?

Last I checked 02 had more roaming agreements than just about anybody. First, they roam in all the countries the US has embargoed other than North Korea (Iran, Cuba, Syria (which has some US roaming partners). It will work with more airplane networks, and ferry network. An 02 SIM will work in a Thuraya sat phone which ATT will not.

That said, ATT has roaming agreements in 215 countries and that ain't shabby. Of the non-contract SIMs you can get, Mobal is the only one of the few that truly behaves like a contract phone. It works in countries where you can't trigger a callback and you don't have to pay for a contract burning minutes in a country you are not in to get this roaming. I looked at Orange's list and it didn't look as extensive. The number of countries looked shorter and I noticed that it didn't roam in some African countries or the Bahamas. I didn't do an exhaustive look:

http://www2.orange.co.uk/servlet/Sat...ame=PersonalIR

To the extent you want to take issue with my punning about gold, give me some literary license.

Does O2's SIM behave that differently if it's pre-paid vs post-paid?

Yes, but Mobal follows the contract roaming. They reserve money against your credit card like a hotel does that guarantees payment of several hundred dollars and they let you use the Mobal SIM everywhere. A prepaid 02 SIM is much more limited. Mobal is targeting the business traveller who just "expenses it."

The part about them reserving money against your credit card makes little sense as I've used Mobal with a pre-paid credit card plenty of times before.

Also, is there any reason the Mobal rates are so much higher than standard O2 UK rates? 80 US cents per SMS is very high & so is 14 cents per 10 kilobyte (14 $/MB). Do they charge this much just because they can (like all data & SMS roaming charges are) or is something else at play here?