There is a difference in cooking with either one, but, done properly and with experience, you can turn out excellent product with either cooker. As a person who owns a kettle and a UDS, I would gladly add a WSM and a PBC to my cooking tools. Each one cooks a little differently, allowing for more flexibility.
I think the process differences are quite clear, once you understand each cooker. I totally disagree with people who say you have to pay lots of attention to a kettle and little to a WSM. I can setup and run my kettle for 4 to 6 hours with no intervention. I would do the same with a WSM. The end product is also hard to distinguish, I can produce great product off of either one. But, the WSM footprint is MUCH smaller, relative to amount of food you can produce.
the meat thermometer was so far past the top reading, it read Taylor
"perhaps...but then again...maybe not..."