In addition to what David said...
You will have a built in heat sink while the plug n play model uses ambient temp. You also won’t have another piece of equipment keep up with and the capability to have 2 meat probes, 1 for programming use and one meat only OR, if you smoke by temp only or time only 2 built in meat probes while only 1 with the plug n play. As far as price difference goes, currently the plug n play is $278 while the difference between the Smokin-it Big Red model is about $225. Having owned both, I favor and have chosen the Big Red Smokin-it upgrade in my case, but would also favor it if I were purchasing a new smoker.