It’s hard to say which one is better, as we’re not comparing apples. Let’s break it up to the strengths and weaknesses of each method.
RTMP used to be the de facto standard for live streaming. Many CDNs offer delivery that scales to the masses. RTMP, however, does not take into consideration that broadcaster and viewers might have internet connections that aren’t always up to the task of transferring the stream at full speed. Smartphones and web browsers are also unable to play back RTMP natively; Browsers used to depend on a flash plugin for playback, which has been phased out over the last couple of years.