<p>[This is a rewritten cross-post from the Oxford/Cambridge thread, but appeared directly on topic to the OP's question].</p>
<p>They offer VERY, VERY different undergraduate experiences. In the UK, students specialise much earlier than they do in the US (an upper sixth former will rarely have more than 4 A-Level classes, and if you are scientifically minded they might be Maths, Further Maths, Physics and Chemistry - so there can be none of the traditional "humanities" after age 15 or so).</p>
<p>As such, when the student gets to university, they will usually know precisely what they want to do and they are unlikely to take much outside of their department. A physics major may end up taking no classes outside of physics.</p>
<p>Whereas most US institutions offer some version of the "liberal arts", where physics majors are encouraged to take say a quarter of their classes outside of their department (or at some schools more), in an effort to make a more rounded individual. To make room for this, most US Bachelors degrees take place over 4 years as opposed to the 3 year British degree.</p>
<p>Therefore, the key question is how focused are you on what you wish to study? This is particularly important if you are choosing a field of study that was not offered at your secondary school (which can be Nanotechnology, Political Science, Archaeology, Architecture, Philosophy heck most courses of study are not realistically offered in Secondary School). And even if you do know that you have a passion for Chemistry, for example, then do you want to major in Chemistry or in Chemical engineering???</p>
<p>And that is key. If you are accepted at Oxford to read Philosophy and after a year you realise that philosophy is just not right for you, then you have to withdraw and apply again for the following year to study something else. Whereas at most US universities, you are accepted to the university rather than the department, so change is possible (again there are exceptions to this - often around engineering departments).</p>
<p>Really figure out what sort of an education that you are looking for, then worry about the rest of it.</p>