an original factory unlock can work anywhere in the world without any tension.
obviously the cost is high because these phones are "pay as you go" and directly from apple store.
company factory unlock are phones which are on contract and later provided with codes to factory unlock them... because iphone is not a very old phone, it means most of these phones are illegal and later forced to unlock it.
both will work... but the later one, if accidentally gone to the county of origin, will lock up instantly because the iemi number is enrolled as stolen in that country .. and might also get you into trouble with the police.
that is why some ppl get the iphone4 for 30,000 some get it for 45,000 some even 75,000. all depends on which grade u going for.
