This is best done as a two-day hike. This way you can spend the night in a very nice and well equipped mountain hut Rifugio Barone and do a short side hike to Lago Barone (30min away) or further on to Pizzo Barone (add another 1h to get there). Lago Barone is one of the most impressive mountain lakes in the area and is definitely worth a peek, or a short swim if you don't mind extra-cold water. The first section of the hike from Sonogno to Seccada and Cabioi (1h from Sonogno) is very flat (in fact you can even arrive close to Cabioi by car) and offers nice views of the valley and the river. Then you start a relatively steep climb that never really gets any flatter until you reach Rifugio Barone. You go past Corte di Fondo (1.5h from Cabioi) and throughout the whole way up you are out in the open and can enjoy spectatular views. This is very different from the hikes starting in the lower parts of the Verzasca valley where a large part of the way up is usually done in thick forest. What you prefer might also depend on the weather. On a hot day a forest can offer nice protection from the sun. The second part of the hike starts with the 150m ascent from Rifugio Barone to Btta. della Campala which offers magnificent views both back at Val Vegorness and forward at Val di Prato and Val Lavizzara. The way down towards Val di Prato is even steeper than the way up to Rifugio Barone. Most of the way lets you enjoy the views although some parts go through the forest, especially in the lower section between Campo Tencia and Prato-Sornico. At the altitude of 1200 starts a paved road so the last hour of the hike down to Prato Sornico is very easy.