Question : What is The Difference Between
Vedic Astrology and Western Astrology?

The most major difference between the two systems is that Western Astrology is based on the Sun, while Vedic astrology is based on the Galaxy – which the Sun is a part of. The Western Zodiac is no longer accurate in relation to the actual stars of the galaxy, instead it is a theoretical Zodiac based on the position of the Sun relative to the Earth. It is accurate in that regard, and can be useful for gaining information pertaining primarily to the Sun: your ego and inner psychology. But it is not very useful for practical predictions. The Vedic zodiac, on the other hand is true to the galaxy itself, which includes the sun and is therefore extremely accurate at it’s core and can deliver reliable results both in terms of psychological analysis as well as practical predictions.
The Western Zodiac was calculated about 2,000 years ago on the basis of solstices and equinoxes in relation to the position of the Sun over the tropical latitudes. Unfortunately, the Earth has a wobble in it’s axis of rotation, which over the centuries has caused the Western Zodiac to get out of sync with the real Zodiac constellations by more than 23º (almost one complete sign!). This is not an opinion or a debatable point, it’s just a fact which you can verify with your own eyes by looking at the sky.
In a liberal sense, the Western “Tropical” Zodiac is in sync with the Sun and thus does have some accuracy. But from a practical and objective point of view, it is extremely flawed. So don’t be alarmed if I tell you that your Sun sign is not what western astrology told you it was. Remember that we are doing this reading through the Vedic system. Your western sign surely has some merit, but I’m sure you will find that the Vedic reading will be categorically more profound.
There are some other differences between the Vedic and Western systems, too. If you are not very familiar with Western astrology, most of these might not make much of a difference to you – but just to mention them:

The exact degree of the rising sign that is on the Eastern Horizon is essential to both systems. It becomes the “cusp” of all the houses. In Western Astrology the cusp is considered the beginning of the house, but in Vedic astrology it is considered to be the heart or most sensitive part of the house – and in some calculations it marks the center of the house.

Vedic “aspects” between the planets are very simple compared to the Western system of aspects. I won’t go into detail, but don’t attempt to use Western aspects to get accurate readings from a Vedic chart.
The Vedic system makes use of 27 stars amongst the zodiac to fine tune the natures of the signs. This doesn’t exist in Western Astrology. These stars are called the nakshatra.

The Vedic system makes extensive use of “harmonic divisions” of your birth chart. Which are new charts created from various ways of slicing up the original birth chart – and which give additional information and detail regard the karmas in the horoscope. This does not really exist in Western Astrology.

The Vedic system makes use of “Planetary Periods” and various sub-periods to be able to tell you not just what is coming into play in your life, but also when it will occur. Western astrology does not have this, though it does make use of yearly charts and transits, as Vedic Astrology also does.

The Vedic system includes astrological gemology, mantra therapy, color therapy and many other systems for adjusting the effects that the planets have on our lives. Western Astrology does not, and perhaps this is one major reason why Western systems are generally more fatalistic than Vedic Astrology, which stresses that you are ultimately the architect of your own destiny.