Let’s step back and examine why it matters if someone is a “gadol” or not.
Ideally, each person should learn shas and poskim, learn up a sugya, examine an inyan, and decide for themselves what the halacha is in a given circumstance. Unfortunately, most of us do not have the time and opportunity to do this so we rely on asking others. If you are not qualified to answer a question, you should find a Rebbi who is, and learn from him what to do. Similarly, if you live in a city where there is one clear-cut Rav of the city, he is considered your Rebbi.
If you do not have a Rebbi, or your Rebbi does not know the answer, only then would you turn to the gedolim. (see Teshuvas Harashba, Chelek Aleph 253). If there is a majority, you would follow the majority. If there is no majority, then “if you know” that one side is “gadol b’chochma u’b’minyan” (minyan here refers to number of followers/talmidim) and that side has a reputation as such, then you follow that person(s). (Id.) If you do not know that one side is greater, then by d’oraisa you should go l’chumra, and by d’rabbanan go l’kula. (Id.)
Thus, the relevance of whether one “gadol” is greater than another, is limited to the above (hopefully) rare circumstance.