Peach trees trained to modified spanish bush (MSB) and Y-trellis (Y) were evaluated and compared in the Mediterranean settings of southern Italy. The observations included two peach (Rich May and Summer Rich) and two nectarine (Big Bang and Nectaross) cultivars. In the MSB system, trees were spaced at 4.5 × 2.5 m (888 trees/ha), whereas in the Y system, trees were spaced at 5.5 × 2 m (909 trees/ha). Costs at planting, yield per tree, fruit size grade, unit price of sold peaches for each size grade, amount and cost of materials and labor for cultural management, and grower’s profit were quantified throughout all 6 years from planting and at full crop (year 4–6). Fixed costs of the MSB system were 45% lower at planting, 11% lower for fertilization, and 33% lower for pest control than in the Y system. Regardless of cultivar, the MSB system reported 19% lower yields, 29% less management labor, and 12% higher labor efficiency (kg fruit/h) than the Y system. The yield gap between the two systems tended to decrease after the 5th year. A greater percentage of fruit fell into large size categories in the MSB than in the Y system. Fruit unit value and yearly profit were similar in the two systems. Even for the most profitable cultivar under the Y system (i.e., Nectaross), the time needed to pay off the additional investment for establishing a Y by its additional profit was ≈11 years, indicating an advantage of the Y system over the MSB only by the 12th year from planting. Yield trends, along with the high initial investment and management labor and costs in the Y system, indicate better financial performance and more sustainable production in the MSB than in the Y system.