I can't make that decision for you but you've seen wireless internet can be just as fickle as wired.I have Cell C LTE Fixed Wireless but my speeds are so poor. At night it even disconnects while I teach! And I only need 2/2 for this particular job. Maybe I should switch to Telkom LTE? Thanks. I'll investigate. Chatted to RSAWEB (Sorry, I didn't know where to post this as the posts were mainly about Octotel) and found out that they are sister companies with offices in Sea Point. Owned by the same umbrella company, RAMP. They are literally one office floor apart from each other.
I can only tell you what I told @AfricanTech when he asked for advice about the same thing. Sadly getting internet in SA is a lottery. Based on whether your area is congested or not and since that information isn't public its really really hard to give anyone a definitive answer about whether they will get good internet or not. I'm not even sure if the companies themselves know half the time. The congestion however extends beyond just fixed providers, wireless towers too get congested.
Best I can give you is that from what I've seen almost no one from Sea Point has been complaining about Octotel.