This subject always seems to produce polarised views. Those tending to support the standard suspension in the main have never had a top quality replacement set so they are a bit in the dark to know what it is like, bit like the Dacia Duster driver happy with the handling and comfort of his wheels when you tell him how splendid rapid and comfortable your Quattro is compared to his unless he drives your car or similar car, he will never know there are in fact better wheels out there like your Audi.
JS
I’ve experienced good quality bike suspension, most recently having had a complete custom set-up by Revolution Racing on my Firestorm (a bike famed for its built-to-a-budget OEM set-up). It involved a custom built Penske shock and a complete re-spring and re-valve of the front. The set-up included me getting onto the bathroom scales in full kit so they knew the weight to set-up for and defining that I wanted it optimised for, which was fast road work. The difference was stunning! The improved way the bike handled fast sweepers transformed the bike and made it as quick as bikes with considerably more power while installing the rider with total confidence. The bike was even used on an Old Gits trip (by and American friend who is a very similar size/build) and while it was on the trip with K1200S, K1300S, FJR, a Suzuki GSXR1000K8 and a number of other bikes, it was, by far, the quickest bike on the trip.
That all said, ride the bike on a bumpy back road (as I have near my home in Suffolk) or around town with potholes and speed humps, and it was a real nightmare.
The point I’m trying to make (in a long winded way) is that good quality non-ESA suspension is excellent, but limited by the lack of on-the-move adjustment! The OEM ESA kit on the K1?00S is all right, but nothing special, however, I would suggest that the ability change modes on the move according to riding style and surface conditions make the OEM ESA a much better choice for real world road use for most riders.
For me, ESA is now an essential. When buying my K1300S the choice was between that and an Ohlins fitted ZZR1400. The Kawasaki won on just about every criteria I had (although only be a very small margin in most cases) however, the ESA, or lack of it on the ZZR, was what swung me to the K1300S.