re: What is the Best grilling smoker

All of them can grill. I grilled hamburgers on my Green Mountain grill last night and they were great. Some manufacturers have added mechanisms that allow you to easily expose the meat to the open flame of the grill, which provides for high heat searing/grill marks. Some people prefer to transfer their meat to another gas or charcoal grill for the searing function. I personally think that's too much trouble and instead would just start the meat on my charcoal grill for meats that are typically "grilled".

I would recommend thinking of pellet smokers less as smokers and more as outdoor ovens with easy temperature control that will impart a bit of smoke flavor on your low and slow cooks. Smoking is not their strong suit. Ease of use is their strong suit. And all of them can cook burgers just fine.