Like to eat while on display, with the entire passing world gawking at your menu choices? Pull up a sidewalk seat on Newbury. Prefer to dine discreetly en plein air, where you can focus on the meal, the company, and the cool breezes? Settle in at Harvest’s soothing garden retreat, tucked into a hidden nook off Harvard Square. Kick back among the sun-dappled linden trees and order a plate of chef Mary Dumont’s salmon with green garlic, or the tea-marinated duck with rhubarb. Then try to decide which is more restorative: the food or the setting.