not all 4-bars are the same.
the biggest difference i notice is brake-jack – this is a fundamental feature of single-pivot bikes.
some people like brake-jack, as it causes the back end to compress during braking, some people like the way that this balances brake-dive at the front.
even some 4-bars have brake-jack.
personally, i don’t like it, your opinion may vary…
a simple single-pivot will tend to be less sensitive to small stuff than something with a linkage – at least, this is what the maths would suggest.
try some different bikes, take the time to fiddle with them to set them up properly, and see what differences you can detect.
some people claim not to notice brake-jack, i don’t know how.
but then, i can’t honestly say i’ve ever noticed pedal-feedback, which is something other people get quite worked up about.