I like what I read about each of them having a different meaning or function. I wouldn't really rate one over the other- they all occur in every chart. The outer planets certainly play a role as well, esp if heavily aspected. If you are talking about the physical body, the appearance of the person, esp the face/head, then you are talking about the rising sign. Also how personality is expressed through the body. If you are talking about ego then this would be the Sun. I think that the Sun sign also shows how we have fun/what we find fun, being the ruler of the 5th house. Of course there is other symbolism connected to the Sun. The Moon is our emotional nature, how things "feel" how we respond instinctively. among other things.

Some suns and moons (and other planets) are more or less evident depending on their house placement. For example you KNOW when you meet someone with an Aries Sun in the 1st. A very independent, dynamic, even martial ego shown vividly through body movements.

A Sun in an 8th or 12th house might not be noted at all until you really get to know the person. A 12th house Sun could really "shine" behind the scenes- as a confidant, a hospital worker, psychic, etc.

Anyway, there is ALOT that could be said about this... there are whole books about Sun, moon rising sign.

The "core" person is all of the planets, all of the houses, all of the aspects, and all of the progressions of all of the planets that determine who we are.  To try to say that any one or two things is the "real" person is very limiting and doesn't even begin to see the entire person.  We are not a part of our charts, but the sum total of the entire chart.  Then, the sum total is changed by the progressions as we learn, grow, and meet life.  So what you were born with is not who you are after decade or two of life.  To answer why you feel you are more Aries than Scorpio, or whatever, look at your chart progressions to see who you have *become.*

I was taught that the ascendant is one's mask, what we show people.

One way I look at the sun, moon, ascendant.  The sun sign is the mind when awake-eyes open-Present day consciousness Left brain. The  moon sign is  the Right brain visual,  instinctive and intuitive.  Very important moon functions are memory, memories and the dream state.  Past consciousness maybe. In this senerio  the ascendant is what you are becoming, what you need learn to incorporate into your being for future growth, Future consciousness.  A person often attracts other people who have planets in the persons ascendant sign to learn from them and grow even if the person they attract shows them qualities of their ascendant they don't want to incorporate.