Yip I have to agree here. Voda's 3G/HSDPA has not been anything to write home about lately. Have been using MTN for about a year or so, but with the cheaper Voda rates I had to give them a shot again.
However the problem is one can't download anything big (over 10MB) at a constant +120KB/s speed on Vodacom. Don't know if they're overloaded? If you do, you're just lucky and may just have found a nice 'gap'.
MTN speeds seems to be much better in my area. Also less disconnections and STALLS (data just stops).
Well that's why I still keep my collection of MTN sims.