Of course good doctors can come from any medical school. Indeed some of our very best doctors are from schools outside the UK.
Stranger is right though in that some schools run courses which have a greater emphasis on academics, whilst others have a lot more early patient contact.
Which is best for a particular student is up to that particular student. So my dyslexic DD is probably better off at a University that does not require weekly essays, whilst she really enjoys, and gains a lot from, patient contact. Her course fits well with her strengths and weaknesses and I expect her choice of specialisation will do the same. And that this specialisation will be no better and no worse that a specialisation that suits someone who is highly academic but who perhaps does not enjoy patient contact. (A friend of mine was like this. He studied at Cambridge, and hated a spell at Great Ormond Street : patients were bad enough but worried parents were worse. He is now a leading researcher in diagnostic cancer radiology in the US.)
Which is "easier" to get into is also moot. Bristol, where DD is, gives out a lot of contextual offers, so might look easier. However from DDs private school where virtually everyone took at least 4 A levels and around 75% of these were at A*, a place at Bristol was considered a real achievement (this was in the days when Bristol did not use UKCAT and relied heavily on PS) as the competition was huge and very academic kids had no particular advantage. Most of her peers went to BMAT schools.
It's not that hard. Some schools give a good deal of weight to academic performance, others, Keele is one example, may have a lower academic bar but will be looking for other things.
In short, those with a long stream of As at GCSE, and who like the idea of three years of academic study really should consider Oxbridge...in part because it may well be as easier to get a place there than it would be somewhere with different selection criteria. Ditto a string of As won't get you far in many places if you have a mediocre UKCAT (DDs problem.)
I would still argue that an intercalation year can help deliver an interesting middle ground. And fun. Though not necessarily in the normal MN "drinking and snogging" idea of fun. DD finds learning cool, and expects to enjoy the year, in part because it will be a challenge and a real change from what she has done so far.
I would add that Stranger's DC's school seemed to outperform DDs school in terms of their success with medical school applications. My understanding was the school often had a couple each year, out of possibly 20 or so, who wound up with no place despite a likely 4xA* prediction. This certainly happened in DDs year. It is competitive and there is an element of luck. Applicants were encouraged to see the whole thing as a two year application. Reapplicants to medicine often do better as they have previous experience of the process and a year's extra maturity.
Stranger is right though.
Parents should encourage DC to find a good fit but not to dumb things down if they have the grades and the sorts of attributes that the schools are looking for.
On top of the sort of course, and the scope for intercalation, there are a whole lot of other factors. DD really likes Bristol. Interesting range of experience, some very good hospitals, some glorious countryside, and more hills and fewer tourists than Oxford.
I would recommend looking at distance from home. Far enough but not too far, is good. My mother died a couple of months ago and it was really lovely that DD was able to join us the night she passed, plus come home the next weekend and then for the funeral. Ditto it was nice that she could come home for a break during her first term, and during a period of illness.
They will also have individual reasons. The fact that Bristol seem to take relatively few from the more academic private schools suits DD. She is the only south-eastener in her friendship group and they do things like camping in November, or surfing. (I know!) There is plenty of social life but different from the sort of experience her friends at Oxbridge are getting (where some appear to be struggling to move beyond existing London social circles), London (though DD would have been quite happy to go there had she got a place), or indeed the sort of student life mumsneedwine describes.
Its all about fit. Apply to the place that feels right, as long as you meet criteria, and it probably will be right.