Like does it mean someone with and account say
Activity;50
Merit;87
Post;51
Has more quality post or is a better poster than someone with say
Activity;100
Merit;87
Posts;150
From my observations, Possibly, the first account holder gained more merits as a result of his or her contributions with good effort posts either answering newbies or discovery of errors or lapses which makes them get more merits. While the second possible had low efforts post which did not really yielded merit for them.
I think sometimes it is also as a result of boards where some majorly post. There are some boards where attention is not given much so in that aspect the possibility of getting merit rewards for a quality post there is small only if one applies for meriting through any of the merit source threads.