The H10 is the gold standard for HRMs and the one most commonly used by anyone doing experimentation with HRV. I don't have the specs memorized off hand, by my recollection is that it does a better job of capturing the entire waveform.
Yep that's right, and the H10 is able to stream the ECG waveform. For this project I used the inter-beat-interval that is sent however, as it means I don't have to run peak detection on the ECG to get heart rate.