I'm not really sure how to answer this question.

For the medieval period, a sword was a prestige weapon. It took extra metal and a skilled smith to craft. The people who had the money to wield a sword thus also probably had the money for other things like good armor, as well as the leisure time to train and a retinue in battle. In the later Middle Ages, it also meant that your enemy was incentivized to capture you for ransom. Additionally, since martial prowess was considered an important trait, literary sources cannot be trusted to provide accurate reports.

So, even if we were able to differentiate objective or subjective skill with a sword, there are a whole heap of other considerations implied by the fact that a person is able to afford a sword which would make him more likely to survive a battle. I don't see how these two things can be separated. I also thing this general difficulty stretches beyond the medieval period, but I can't speak to things outside the borders of my own knowledge.

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, you may PM /u/caffarelli to have your question considered for an upcoming Tuesday Trivia thread.