Jayco or Grand Designs toy haulers experience?

As with any of them, you have to find a floorplan that works for you. Having kitchen cabinets that are easily accessible, without a stepstool and with some depth are important to us. Similar to 12" deep cabinets in your house. Some models/brands have nothing close. I personally wouldn't buy the Jayco because of the slide system they use on their large slides so between the 2 you mentioned the GD would be the better choice in my opinion.