Well, this is an easy question (sort of). Of course it compromises the clinical training. Think about it this way, someone with 3000 hours of relevant experience is probably not as good as someone with 4000, other things being equal. Some of this is offset because the learning curve is steeper at the beginning than it is in the later years of training, but a difference is still there.
But it's the wrong question. The proper (and much harder) question is: which do I need more?
- the skills that would be compromised by a shortened residency/fellowship, or
- the additional skills that would be gained by extra research time
Because you can only have one. That extra year of research time would make a huge difference too.
To answer that, you have to ask what kind of career you want or think you are likely to have. If you think you are going to do 80% research at a big academic center, have a half day of subspecialty clinic a week, and attend on service 2 weeks a year, then the research track is for you. If you expect you will want to do any significant amount of general work (general neurology, internal medicine, whatever), then the balance shifts. The problem is you have to take into account where you want to live, what kind of salary you want to make, and even what kind of jobs might be available in 10 years.
My advice: Take your best guess, and if you're headed into academic medicine take whatever shortcuts you can because you've already been training too long.