In US, students have to take course work while they are doing research...this helps in building basic concept and fill the deficiencies. While in UK, there are no classes and there are no well-defined research projects for international students. And they are told "to do what they want". Do not you think US approach is better. Can anyone also comment on the duration of PhD in US vs UK.

you already have an Msc Dina. that's what they would probably be teaching you in the US. Just revisit them notes you made then.

As sweetchic said, u already have an MSc, u don't need lectures anymore and if u want lectures u can always attend the MSc ones which are open to PhD students too. In USA a phd takes longer, so depends how long u r willing to work hard for