Just finishing a Kosmic Lynx 32mm chassis with a Stock Moto, 1999 CR125, so this topic is very fresh for me. Here are my thoughts:
1. Chose the stock moto because it is a popular class in the Northwest.
2. The Kosmic Shifter chassis is designed for the ICC package and fitting a stock moto is more work. Many times I almost switched to the ICC rather than continue the fitting of the moto engine where it was not intended.
3. Stock Moto parts are cheaper, a lot cheaper.
4. The Stock Moto seems to be a very durable package and a little easier to tune.
Have not been to the track yet with the new kart, still sorting it out. Hoping all the work will be worth it. Would I do it again? Not sure – installing the ICC would have been a lot easier.