Full disclosure; I worked for both Telerik and Infragistics in Developer Relations for these projects. From my point of view, neither is a clear "winner" in this space. Kendo has some nice features and Ignite doesn't have and vice versa. We ended up picking Kendo because we needed to settle on one of these, and most of our clients already owned Kendo because it came with some other Telerik product. That's it. It could have very easily gone the other way, but Telerik kinda won the ground war here, so...

Having said that, the only tool we really use is the grid (the rest of them are no better than Flowbite/HTML5/etc. controls. And even then, we really need to be leveraging the advanced functionality of the grid before telling the client they'll have to buy a support license.