The answer to your question is yes the path to doctor in Europe is slightly shorter. The European system takes kids right out of high school who have passed exams called the "A" levels and puts them through a 6 year curriculum in which they get a MBBS which is a bachelors degree in Medicine but is equivalent to an MD. If you practice in the US you will be an MD. The only thing they miss out on is some of the liberal arts you would receive by getting a bachelors first and an MD later. However you can do something very similar by going for an accelerated program in the US in which you get both your bachelors and your MD in 7 years. Or you could accelerate yourself by taking summer school and getting your bachelors in 3 years. Your residency options might be somewhat more limited by getting your degree in the UK just because you may have not made some of the contacts with US hospitals you need to get a great residency. But your education will be first rate. If you are very young, the added maturity you get from a few more years of schooling may help you to deal with the sick and the dying patients. There are no more classes you will have to take to get licensed in the US. I believe you will have to take a test to verify your command of the English language. This is very hard to believe but I think it is true for all foreign grads. By the way the schools in Ireland actively recruit Americans for their 6 year program through the Atlantic Bridge. Also check out schools in Australia which are very good too.
Finally it is always easier to go to school in the US. You will not have any worries about being prepared for the USMLE, you will not have to take any silly extra tests. I would only go the foreign route if you have an adventurous streak in you and are willing to put up with a few hassles and are not looking for the most competitive residency programs (like dermatology or radiology).
