Vedic astrology is much like Western astrology. In most ways they are the same. There are, however, a few notable differences.
To begin with, Western astrology originated in Greece and was influenced heavily by Egyptian astrology. In general, many ancient Greek systems of thought came from Egypt or were at least influenced by Egyptian systems of thought. And there are many cases of Greek philosophers spending time in Egypt learning from their thinkers.
Origins aside, Vedic astrology and Western astrology are very similar. They both have the same 12 houses and the same 12 signs. These houses and signs have almost identical meanings in both systems. The planets also have the same meaning in both systems: Jupiter represents expansiveness and religion, Saturn is discipline and restraint, Venus is beauty and love, and so on.
The positions of the planets, however, do change from one system to the other. Planets in Vedic astrology move approximately 23 degrees back in the zodiac from their positions in Western astrology. For example, in Western astrology on March 21st the Sun would be at 0 degrees Aries but in Vedic astrology it would be at 7 degrees Pisces (as Pisces precedes Aries in the zodiac).
So which one is right? Astronomers agree with the placement of Vedic astrology because it is scientifically accurate. The stars, as observed by astronomers through telescopes, align exactly with where they are said to be in Vedic astrology; both astronomers and Vedic astrologers would agree that on March 21 the Sun is at 7 degrees Pisces.
Why are the planetary positions of Western horoscopes not scientifically accurate? There are two explanations.
Western astrology claims that the Sun moves into Aries on the first day of spring (March 21). This is true, they claim, because Aries represents new beginnings and therefore the Sun must move into Aries on the first day of spring (which is roughly the day when winter ends and new life begins).
There are two problems with this explanation. One is that in the southern hemisphere, March 21 is when everything dies, as winter is in June, July, and August (and the fall is in March, April, and May). The other problem is that even in some countries in the northern hemisphere (like India), March, April, and May are when the temperatures rise to even 115 degrees and all plant life seems to die and turn brown. So for much of the world’s population, spring (March, April, May) is a time of death rather than of new-beginnings.
The other explanation for why the planets are 23 degrees past where they should be is that scientifically the Western astrological placement of the planets was correct perhaps 3,000 years ago when it was first developed, but due to ignoring the precession of the equinox (based on the earth’s tilt) their position has changed very slightly every year until, after several millennia, it is 23 degrees in error (and that error will continue to increase over time).
Whether or not one adopts Vedic astrology over Western astrology is a personal decision, but I do think it is important to recognize that significant scientific error calls into question the veracity of Western astrology.