McDonald’s is gone from Porter Square, to be replaced by a Qdoba Mexican Grill franchise, another nudge from the invisible hand that wants the area to become a mecca for Mexican food as well as Asian cuisine.

Qdoba falls into the “fast casual” food category, which means it’s slightly fancier than its putative competition in Porter, Anna’s Taqueria (right across the street in the Galleria) and Tacos Lupita (a fair stretch down Elm Street in Somerville). Some Qdoba locations can serve alcoholic beverages. It’s also more expensive; while the highest-priced items on Anna’s menu are “Mexican plates” of rice, meat or vegetables, beans, corn tortillas, salsa and hot sauce, Qdoba passes that easily with just the price of a basic quesadilla — meaning just cheese, pica de gallo and possibly unwanted sides of guacamole, sour cream and salsa. The difference: $3.95 for a “plate” at Anna’s, $5.39 for a quesadilla at Qdoba.

For a quesadilla-to-quesadilla comparison, Anna’s charges $2.95 for a steak quesadilla and Qdoba charges $6.79. A side of guacamole at Anna’s is 55 cents, while Qdoba charges $1.19.

Qdoba is competitive on tacos, though. It charges $1.79 for a grilled veggies taco, while Anna’s charges $2.05. A steak taco at Qdoba is $2.19, or $2.05 at Anna’s.

The differences implies there needn’t necessarily be war between the restaurants. The presence of Qdoba may thin out the crowds at Anna’s slightly — not a bad thing from a customer’s perspective — but mainly by removing the element who’ll shrug off the doubling of the cost of a quesadilla.

That Qdoba boasts of having “vegetarian” fare may also finally convince Anna’s to move on from boiling its rice in chicken broth, when vegetable broth would do just as well.

It may also help the McDonald’s crowd. Those who come hoping to find McDonald’s may wind up eating healthier. Or maybe at least having to walk to Davis for their Big Mac and french fries.