If you decide to bring the twin beds with you make sure that you bring enough bedding for the 2 to 3 years you are planning on being here, since the beds here are smaller you may find it difficult to get sheets to fit. Also I find the quality and price and selection of bedding in the States much much better than here.
You haven't mentioned your bed. I just wanted to give you a heads up that it is not just the twin bed size that is different here. Basically a US king is a super king here, a US queen is a king bed here, and a double bed is a double bed.