David Moore (X) Feb 25, 2014:

To, or on To my ears, "on" makes no sense, and is probably one of those mistakes the Internet is so fond of perpetuating. According to google, it loses compared with "head TO head" by less than 50,000 to over 17 MILLION.

Jenni Lukac (X) Feb 24, 2014:

Charles, you've made a very good point. Which term is used in English depends on the context.

Charles Davis Feb 24, 2014:

@ Deborah I'm sure it must be a variant of "head-to-head comparison", which, as Jenni says, is a direct comparison between items, either as a whole or in terms of a series of criteria. So a head-to-head comparison between Messi and Cristiano Ronaldo might consider goal statistics, assists, tackles, etc., looking at how each rates on these criteria.

In medical trials, a head-to-head comparison is a particular kind of trial in which two or more active treatments are tested simultaneously.