A vision can be related to an apparition or a supernatural visage; it is sometimes accompanied with some spiritual or religious meaning, entity, or symbol. While ‘vision’ may be used to describe any mental image being conjured, such as recalling something from the past, or painting a scene while reading, the usage here will be reserved for religious, spiritual, and supernatural purposes.
A vision is not uncommon, but they are less common than dreams, and depending on the nature, are easier to interpret. For example, a common vision is that of a deceased person who assumes an ethereal form, or just a ghost. The understanding of a ghost that has manifested is not like a symbol, while piecing together their life and death without knowledge of who they are can be tricky, their puzzle can be solved with research. A dream, however, can be vague, the symbols one perceives may not be symbols upon first glance, but to the experienced and learned, it will be clear. For example, a box is a basic item, and in a dream, its appearance and meaning is dependent on other things. In a dream, if one is in a box, then it is a sign limitation or a restricted nature. But then that raises questions on the surrounding, if that person leaves the box and is at home, then their home environment is where restriction lies. If it is at a work place, then something is hindering them at work (Stopping their ambitions or desire to excel at work).
In short, a vision is a lot clearer than a dream and requires less interpretation. People may share visions, such as seeing the same ghost at the same place (This is quite common), but two, or even three, people having the same dream would be extraordinary. Visions are also during an active state, while dreams appear when one is sleeping or in a resting state (not including daydreaming).
As for similarities, a vision and a dream tend to be personal, but themes may be similar. And both are important for offering revelations, the clairvoyance, and giving potential insight. However, that does depend on the nature of either the dream or vision. These differences are necessary in order to distinguish what makes a vision unique and special, but both are important in one’s spiritual journey.
A vision can come clear, a non-obscured sign or message (Like in the case of Constantine), but if there is a ghost at the end of the hall, it may not say anything, it may not move, and yet it is possible to learn from the event if the desire to learn is there. The figure (or figures) in a vision may or may not recognize the presence of the observer. But it is possible that the vision has no figures, it could be a message or symbol that is meant to be understood or applied in some way. Explaining a vision may be difficult, but you will most likely have an understanding of what you witnessed. Regardless of that, it is often perceived that a vision can be some form of revelation, depending on what is observed. And treading along a similar line, it may even be a form of spiritual awakening.