It's best stick to the same "technical specialist" if its the actual foreman that get his hand dirty with your car. Then this guy will know what he has or hasn't done to you car before, thus can give you better advice. Rightly say so "Family Doctor"
When it comes to BMW service center, a bit difficult because no direct interaction with foreman and they keep changing anyway, keeping to the same Service Adviser would be the next best option, that is if u can get an attentive service adviser la. Plenty of "chin-chai" SA around that always tell u "We have done something, u test first, if still cannot, come back again la.." kind of attitude. Even Service Adviser also keeps changing but can rely on service history in the computer la.
Getting closely in touch with Sales Adviser, you get Personalised service la. I believe BMW service center have no intention to provide ill service to any of their customers la.