I think you've misunderstood the question. OP was wondering if the 8 years of undergrad + med school in the U.S. was better or just less efficient than a 4 year medical degree from India.
However, thanks to your posts on the topic I think it might have answered a lot of the question.
For one thing, we know that a lot of undergraduate things aren't necessary for med school. I have business and music majors in my class who, while may be at some disadvantages, are overall doing just fine academically. The true requirements for undergrad would take less than two years if one went to school just for that. The rest of the time is unnecessary for anything other than proving oneself. CDI said above that there are high attrition rates and low acceptance rates for Indian med schools. I don't think this proves that they are any "harder," given the weeding out process of U.S. undergrad programs. I went to a no-name state school that puts out about 5-10 med students a year, compared to 800-1000 students that identify as pre-med when they enter freshman year. I'm sure there is even more students who are considering medicine that just don't identify themselves. I don't think that students at more prestigious schools have such a high attrition rate, but it still has to be there. Of course, once we get into med school, we are almost guaranteed to pass.
Ultimately, yes, the U.S. system is obviously inefficient, but I don't think it is designed strictly for efficiency. I think the goal here is to get well rounded, mature people into medicine who will have a life long commitment to their job. I know it doesn't always work out that way, but it seems to be our goal.
I understood the question just fine, and OP also asked the Pros & Cons - which I decided to address as well. Simple answer to the first question is obviously, "They don't pack in a 7-8 year experience into 4 years. It's apples to oranges." Which I guess, looking back, no one had actually answered till now. And now looking at OP's original question, I realized that the question itself isn't accurate, as there is no "4 year" medical degree program in India, unless they are referring to the hybrid India/Carribbean/US programs, in which case I'm not sure the exact length.
My previous response about the poster not understanding that last question, was in regards to a
specific concern of the OP about why US students have difficulty finishing on-time. The poster did not answer or address this question, and instead answered the original question at hand. Please see that statement for clarification.
Regarding admissions/pass out rates, etc. I was just giving an example of how difficult it is to get in & out. Obviously med school itself is tough, and comparing the two is difficult, and not really fair. It ultimately comes down to what one is looking for and what their final goals are. The two systems are still two very different beasts. However, we can lay out what we do know.
In the US it is VERY difficult to get in, no doubt about it. However, the pass rates are practically automatic as you've mentioned. And yes, the "weeder" system starts picking people off early in undergrad, so by time of admissions the competition is already extremely high. However, in the US, many take an extra 1-2 years, to pad their resume, and then get in. Many even much older decide to join med school.
The Indian entrance is essentially based off of one entrance exam. Students join into the chosen track at the age of 15. They can't do a liberal arts degree or major in poli sci if they choose to
TRY to get into medicine. They are strictly in a medical/paramedical track for the 2 years prior to taking the medical entrance exam. All 70-100,000 (each state is different) students then take that exam and it ultimately ranks you into which school you will attend, if at all (depending on the state). As you can imagine, the majority do not get in. Further, there is no such option to enter med school at a later age. You can not go back and do the pre-req 2 years, and there is in fact an age limit in place.
Now as you can probably imagine, the admissions process for a student from the US is very different from the students who are from India, as there is a quota alloted to such students as well as students in India who are willing to pay a much higher tuition rate (10-20x cost of tuition for a top ranking student, which essentially floats the institution costs and is vital to their existence). Among other things, your HS grades, SAT scores, etc may be taken into account at a more respectable institution.
Also, I think you hit on an important point:
I think the goal here is to get well rounded, mature people into medicine... is something which is lacking in the Indian system and could certainly be seen as an improvement.