I assume you mean counter service?
Time... is what you make of it. A standard table service meal, from arrival at the restaurant to departure, takes maybe 75 minutes (variable, depending on how quickly you eat [and are served!] and how long you have to wait for a table after checking in); longer for a signature. Even at a busy time, counter service will be quicker.
But, there are other advantages to that table service. You're sitting, in air conditioning and out of the sun, and relaxing for that time (minus perhaps some of the waiting-for-a-table time). This can minimize your need to take other breaks throughout the day, which is even more important with the typically shorter operating hours in the winter months. Also, if you are into character meet-and-greets, you can get many of those done while eating, saving you time (and standing around in lines) in the park.
There is a reason, though, that most people recommend doing only two meals per day (one of which being a signature/2 TS meal) when on DxDP - it's not just the time, but also the amount of food involved.