Yeah, the spacing in 4v3 isn't equal. The gaps between the thirds and the middle fourth is twice as big as the gap between the thirds and the outer fourths.
I've never been able to get cognitive rhythmic independence of two voices in my head, so when I play a polyrhythm it's really a single, very fast rhythm with lots of rests.
For 4v3, what I found really helpful was to practice "1-2-rest-4" vs. "1-2-3", then add the middle beat.