it depends on what you want to do with the phone and what network you are on.
I am on MTN, and because they are so smart there, with my i9500 I had my sim LTE enabled and now I am getting 19mb/s download speeds in the office in sandton. the reason for this is the spectrum mtn uses for LTE is 2100 mhz, and the i9500 uses that frequency as hsupa. so with the non lte phone you get lte speeds.
as far as processor goes with the octa vs the double quad its a difference you will not notice. there are kernels out there for the i9500 that allow you to properly overclock the "big" and underclock the "little" that allow you to get 2 days batterylife when not pushed and 2ghz when really pushed.
now for the note 3.
from what I can tell you can get it from vodacom as of last friday and from Cell C as well (not sure from when though) there were articles on this site about it with prices.
from what I can tell all the Note 3's in south africa are LTE, but I could be wrong there.
stock android or even a different ROM for the note 3 will most likely be comming out in the next few weeks, I mean the phone did get released at the beginning of september, so please be patient.
what would I do if I were to buy a phone now? honestly I would get the note 3. Simply because the official release event was on the 4th of september. and vodacom south Africa had handsets with people before october. South
Africa was not last to get a phone, show love and snap it up as soon as possible maybe then more phones will come here quicker (and we mght get a nexus when it is launced one day)