What uniformed CCA is a good one to pick? My son is choosing between NCC Air and NPCC. My concern is that it's just all about marching and more marching. Anyone can share their experiences?

It really depends on the school. Although it's the same cca but some school their teachers are more enthusiastic and will bring to students to the competitions, camps etc that are for the schools on the zone. Some teachers sit on it and only go for the important activities. So u might want to see what activities each cca is going to go for through the year. I was from npcc and as a admin in my sec4 yr I came to know that there were so many invitations but my teachers were just not interested/able to bring the students there