According to some sources, souls differ in chronological age. So-called "Old Souls" have distinctive characteristics that distinguish them from their younger counterparts, including, for example, an advanced level of spiritual wisdom and a certain blasé attitude towards life. Presumably, old souls have experienced enough lives to have been there, done that, all too often. So, allegedly, old souls are more spiritually evolved, having learned more lessons on classroom earth than more junior souls. People who claim to be old souls are typically in the new age movement or in alternative spiritual practices. One seldom hears Methodists sitting in their Sunday pews murmuring about how the Jones' over there are really such terribly immature souls. It isn't uncommon, however, to hear "new agers" talk about other people as being old or new souls. Those on the alternative spiritual path believe, in most cases, that they have outgrown conventional religion, or they never developed an interest in being a Baptist or a practicing Jew to begin with.
However, according to mystics, and some theories of modern physics, time does not exist, and all those incarnations we see as a sequential string of lives are really lived simultaneously. That is, what we think of as time is really a place. Our mind, or ego, just happens to be focused on the one we're experiencing at the moment. The soul, on the other hand, knows what's going on in all the lives and uses that information, according to some sources, to adjust the different lifetimes to reflect the karmic theme it wants to express.
The attainment of spiritual wisdom, the ability to manifest paranormal abilities, and the attraction to non-institutional religion doesn't necessarily mean that some people are living more lives simultaneously than others, nor does it mean that some people have learned more lessons during the same, more or less, number of lives, although those are possibilities. In fact, it could be that those who consider themselves to be old souls, or spiritually advanced, aren't really any different than other seemingly immature souls. All souls are probably roughly the same since they are all sparks of divinity and God is ultimately indivisible.
All is one, and it is only our human judgments that categorize people's spiritual beliefs or capabilities into a hierarchy of spiritual advancement. After all, what we think of as manifesting our spiritual advancement is really a reflection of the mind or ego's functioning. If we were reflecting our real Self, we would be someone like Sai Baba, the late Indian Avatar who could manipulate time and space. So if all lives are lived simultaneously, then everyone is experiencing lives of spiritual ignorance and lives of spiritual wisdom in a place of no time. And those lives of spiritual wisdom amount to some souls only choosing unconventional spirituality in the life they perceive themselves living as a way to learn about God from a different perspective.
So why the need to make a spiritual hierarchy? The ego has an assortment of tricks to keep itself alive and in control. Creating a spiritual class-system is one way to ensure the ego is inflated. After all, it's generally only those who think of themselves as old souls that make the distinction between who's spiritually advanced and who's still in metaphysical kindergarten. So while it is obvious that in the reality you happen to be experiencing some people seem to be wiser, filled with more goodness, and are closer to God than others, in the ultimate sense, they are no different than you. Everyone is a divine soul experiencing different lessons. And that is yet another reason to "judge not."