It's not merely a "slightly" better network. Who decides what 4G is? I've seen it being called anything from 3G to 3.25G to 3.5G to 3.75G to 4G. If there's no clear point where one generation of technology ends and one begins it's just marketing hype. One US network calls itself the fastest network, Vodacom calls themself the leading network, both false claims.
There is no honesty in subjective advertising. I've always said to everybody 3G and 4G are meaningless marketing terms. Vodacom can go suck donkey balls. If they want to waste money on a storm in a teacup rather than upgrade their network to be better than Cell C they can expect me not to be on it anymore, whatever Cell C calls theirs. They should realise the power lies in individual experiences and not what you call your product. Again Cell C's advertising was 4Gs, not 4G. One only need to look at the recent breach ruling where it said what the term stood for to realise the ASA is biased.