Thanks. I see here (
http://phonepricescompared.co.za/2014/04/samsung-galaxy-s5-price-in-south-africa/) that the Vodacom deal has 75 minutes airtime versus 100 minutes with MTN but it has 450MB data versus 300MB data. SMS is of little concern as even 100 are far too many. The extra 150MB data with MTN would be worth R20 (R40 for 300MB) whereas an extra 25 minutes airtime would be worth R35 (R70 for 50 minutes). So the pricing is actually much the same with both companies.
The choice would boil down to the "freebies", with the Gear being far more useful than the speakers. I seriously wonder about the number of Gears given though... it says stock limited and I fear it will not be many and that'd be the only reason I'd go with them. Without the Gear the MTN contract suits me better. I reckon most people will get the free S-covers with only a tiny few getting Gears. The problem is you won't know before committing
EDIT: As an aside, I see an extra GB of data with MTN would cost R90 so neither here nor there regarding the boost either.