Both are very good flight schools, but I would recommend 43 air school. I did my training there, good accommodation, great instructors: most of them are trained at 43 itself, Lots of aircrafts which means an airplane is always there for you to train so you wont have any delay involving engineering problems or unavailability of airplanes, Port alfred is a very small safe and peaceful place and good places for outings are there also. Recently Boeing has partnered with 43, I am not very sure about the new programmes.
Downsides at 43 are, sometimes the weather wont be on your side and the price is on average 80-100 thousand rand more than average SA flight school pricing. Its more or like a traditional college style school rather than a average flying club/school, sometimes you wont have freedom for example sometimes you need to attend ground-class strictly whereas in some flight school you dont need to attend if you think you can self study, you will feel like you are at a college/university. But the flying is great.
I dont know much about progress but I heard at progress you will gain more personal attention from the instructors, also challenging flying and feel more like a flying school but the school can be overcrowded at times and delays in trainings.