This thread is interesting, especially how the subject has changed from the original question regarding strength in Tai Chi to defending one's choice of martial art. That is definitely not the martial way.
Regarding the original question, equal skill would be based on how and why you practice Tai Chi. You can practice it for health, meditative movement, fun, or to advance to the combat stage of Tai Chi training--or a bit of all. The hypothetical situation would probably have to be 2 people who have equal skill in push hands and Tai Chi applications; although, "skill" is very subjective and depends on many factors. Too many to answer this question with one simple answer.
In reference to the comment regarding Tai Chi having nothing to do with combat is inaccurate. All forms of Tai Chi have applications (sometimes several) for each move. The study of applications depends on the stylist's goals and reason for studying Tai Chi. Tai Chi also has many weapons forms. Originally the weapons forms were not designed just for practice but for fighting, combat, defense, or however you wish to describe their use. Recently I have read that Tai Chi is being studied as to how Tai Chi stylists become "stronger" or more affective as they grow older while external martial artists tend to lose some strength as they grow older.
The history of Tai Chi is fascinationg, especially regarding it's influence on all forms of external martial arts and a person's reason for study. I would suggest that anyone who is not familiar with this art talk to a Tai Chi stylist or read something about it. I also commend the Kenpo artist for studying Tai Chi. There are several external martial artists who study with me and say that Tai Chi has helped the immensely. Sorry for the long post, but I felt that some clarification was important.