@dwhitejazz Komplete Kontrol is specifically designed to work with NI hardware, namely the Komplete Kontrol MIDI keyboards - the integration with those is virtually seamless, and third party devices that adopt and use the NKS Standard. You can use this link to the NI page, click on the NKS icon “More Info” for more information: Komplete Kontrol keyboards and NKS standard. Unfortunately NI only list some of the partner companies and not specific products that use the standard, and as you know if you use KK the plugin doesn’t list other party’s devices. However, your comment does say you are using a S-88, so KK was designed specifically for people like you!
The biggest disadvantage to using KK is that you can only use one instance of Kontakt in the Komplete Kontrol plugin - e.g. only one instrument. To me it’s more like a channel control plugin. Of course you can use more than one instance of KK in GP but KK is more resource intensive that just the Kontact plugin. With the S-88 though this may not be the case.
At the end of the day what you use will be determined by what hardware (like you have a Komplete Kontol keyboard or other NKS device) you use, what you want to do with it - KK has some nifty features that aren’t included in just Kontakt - the quantity of plugins that you normally use and type (e.g. VST3s have lower resourcing requirements) and the processing power of your computer/audio workstation.
Hope the above makes sense and helps. One of these days I’d like to get and use one of the KK keyboards - I currently have a Novation Impulse keyboard, so color me jealous. My own experience though is GP is so flexible that I’m not sure it makes much difference to non-NKS users if you have enough horsepower to handle the CPU loading.