Only you can answer that one, but I would say the following matters to me:
1. Reliability. If you are unsure of the Clio RS (or the 208), then do not get it. If you don't feel confident driving around in the car, you won't enjoy it. Don't compromise on reliability to get an automatic gearbox, in other words.
2. Price. It is a difficult one to do, but you will be happier that you did not overspend in 2 years time. That few hundred R difference per month adds up!
Then look at things like an automatic gearbox.
The problem with automatic (or DSG) gearboxes in superminis is that not many cars have them, so your choices become very limited. If you want a supermini with an automatic gearbox, you end up having to either compromise price (new Polo GTI), or reliability (Clio RS or used Polo GTI). If I were you, I'd probably be looking at a slightly used Polo GTI, if not, go for the 208 and put up with the manual.