I have one of each: the Shadow on my 36 and the KH on my 29.
The KH is more easily adjustable for up and down but once the Shadow was set up, I have never needed to adjust it again. They have similar ranges of adjustment, but it is far easier to make minor tweaks to the position of the KH.
The T handle on the Shadow is noticeably wider than the T on the KH. I prefer the wider one.
The Shadow gives you an option of a rear handle too. I cut mine short and used it to support a bottle cage. It also makes enough of an improvised rack to hold a lightweight waterproof top or other small luggage.
The Shadow comes with a narrow seat post so it will only fit certain frames unless you also buy a shim.
The KH only fits certain KH seats, so in that sense it is less versatile.
The direct comparison between a 36 and a 29 is not easy because the 36 is inherently more stable, and also because I do different kinds of riding on the two unis. However, I have consistently felt that the Shadow set up feels more rigid and direct than the KH. I don’t know why, it just does, and it’s a real effect.
After various experiments I now have both of my handles set up just as a T handle without bar ends. I have improvised a bracket for a front light. I have padded the ends of the T handle, partly for comfort and partly to prevent bruises to my legs in UPDs.
I tend to ride easy stuff holding the two sides of the T handle. When tired, I tend to put the heel of one hand on the T and then rest the other hand on the first hand. For uneven surfaces I hold the T with one hand and keep the other hand free to aid balance. For really tricky stuff, I hold the front of the saddle and ignore the handle.
Both handles make a big difference to day to day riding.
On balance, I prefer the Shadow, but they are both good products.