Human beings have a natural preference for whatever system they are used to, and naturally see any other system as inferior.
If you use feet and inches to measure a piece of string, it would be different if you measured the same length in centimeters and meters. Yet both are correct measurements of the same piece of string.
The methodology of vedic and western systems may differ, but both give accurate results when used with correct methodology.
addition: vedic astrology was not known to the western world as most manuscripts/books were written in sanskrit/local languages. It was only in the 20th centurary esp after WW2, that scholars have translated some of the important manuscripts/books into english language, and with the advent of internet, it has become accessible worldwide. Now many western countries have vedic astrology associations and offer vedic astrology accreditations. Now there are many western astrologers who have mastered vedic astrology and written books.. eg Dr David Frawley(astrology of the seers), Dennis Harness (the nakshatras) Andrew Foss,Brendan Feeley, Barbara Pijan, Phyliss Clubb, Dennis Flaherty, Howard Beckman etc etc. There have aslo been various Indian astrologers who have written books in english and given lectures worldwide, including BV Raman, KN Rao, NVR Rao, Sanjay Rath, KS Charak( especially good info on medical astrology) and many others.
vedic astrology is similar to sideral western astrology.
vedic astrology is more than 5000 years old, and originated from the indus civilisation.
It is not the tools that are faulty, it is the expertise of the astrologer which give accurate results.