I don't know of a study that's looked at this formally, so I'm going "off the top of my head". It seems to me that the difference is that if you say "David is fastest", you are implying that David is the fastest among the small group of people that you have seen, but implying that it is likely you would find somebody faster in the wider world. If you say "David is the fastest", you are slightly more implying "He is the fastest among this group and also is not likely to be beaten easily by other people".

Omitting "the" seems slightly more informal as well, to my UK ear.

Superlatives with "the"
What kind of non-technical training course do you suggest for a programmer? Example could be public speaking course, presentation skill, English, business writing, or anything not related to programming or software engineering itself.
