The one technical difference that matters
Western astrology uses the tropical zodiac, fixed to the Sun-Earth equinox. Vedic astrology uses the sidereal zodiac, fixed to the actual stars. Due to the precession of equinoxes, the two systems have drifted apart by approximately 24° over the last two thousand years.
This means: a Western Aries (Mar 21 – Apr 19) is typically a Vedic Pisces (Meena). Same birth, same sky — different label, because the two systems answer different questions.
What the tropical zodiac is good for
The tropical zodiac follows the seasonal cycle — Aries is always the spring equinox, regardless of stellar drift. It is excellent at describing the psychological and developmental cycle of a year, which is what modern Western astrology focuses on.
What the sidereal zodiac is good for
The sidereal zodiac tracks the actual stellar positions. It is excellent at predictive timing through the dasha system — which Western astrology does not have an equivalent for. Vedic astrology can say "between ages 32 and 39 your career enters a Venus-Mercury sub-period; here is what that historically means" with a specificity Western astrology does not offer.
The honest synthesis
Neither system is "right." They are different instruments for different questions. Western astrology will give you a psychological self-portrait. Vedic astrology will give you a timing map. The two are complementary, not competing.
Our reports always state which system informed which insight. You can see the working.