I see it as a business model decision: What sort of place do you want to provide and create? Each way has its pros and cons. Each model of service will be more and less attractive to customers. If you anticipate enough traffic, then wait personnel could indeed payfor theselves in terms of upselling, attracting clientelle, and reducing the workload at the cashier/phone station.
Wait staff also bring added labor costs, management hiring needs, accounting, critical control point for $$$ and supervision. I believe that a top rate and reliable table server is worth their weight in gold in terms of customer satisfaction and driving business.
Make the style of service fit the overall business model you have now, or make the whole thing feel seemless. It would be really odd to have a qsr feeling place (LC, PJ, PH) with white table cloths and a semolier . . . just like having a really high style feeling place with a counter service and paper plates. Have a sense of continuity when you do it, so you don’t confuse your identity in the minds of the customer.