I do somewhat better on Cell C, but not by too much, though it's usable for me ; in fact, my downloads seem (from a sensory perception point-of-view) to be almost as fast on Cell C as they are on Telkom, and I also don't sense pings are any slower when loading web pages.
My Telkom speeds can be similar to yours, but usually somewhere between 50 - 100+ Mbps.
MTN I used to get about 45 / 45 Mbps, but that went away suddenly & had regular cut-outs from their network, daily (via Afrihost, last year).
I'm taking a bit of a chance from the 1st July by getting the 200 GB (100 + 100) Cell C package for R389 (60 days), while still available - might be gone after the beginning of September ?
Had previously thought to get a more balances mix of Telkom & a lower package of Cell C, but this Cell C pricing / data is too good to pass up.
Will keep 10 + 10 GB Telkom going through Axxess, in case Cell C conks out at times, because I double-checked in my router the other day that Cell C only has 4G / Auto (one and the same, I'm sure) available so if that goes, there's no way to use 3G as a backup, unlike Telkom which reverts back to 3G at times (primarily when power outages occur).