I used to look at charts "both ways" all the time. It gave me a headache after awhile, but the way I remember it was that one of the two might be more applicable or better to "go by" than the other, depending...
The use of signs in tropical astrology seemed better suited for determining one's personality than the Vedic system. But in some cases, "destiny", "fate", etc. might show up more strikingly in the Vedic chart.
The easiest example is Adolf Hitler. If you look at just the
rasi (Vedic natal chart), you see 4 planets in Aries (incl. Mars) opposite his ascendant. Of course in Vedic astrology, which is a highly predictive system, an "opposition" is deemed as such simply if the planets are in opposite signs. Degrees are less of a concern, and the same is true for all the other aspects.
But by that system, even a novice could predict, "born to raise hell".

So what I concluded was that in the horoscopes of friends and others with more muted/less distinct karma, they might look more like "themselves" using Western astrology. If someone was really going to make a big dent in the world, you would clearly see it in the Vedic horoscope.
But I don't think either system is limited in either of those ways, nor do I have any real
scientific information to back up my findings.