Earlier quoted context omitted.
It's been shown to be less infectious. Mortality rates are the same for both strains.
No idea what original article I read now that compared mortality rates, but I'd suspect it used this analysis as it's source: https://www.cato.org/blog/two-supertypes-coronavirus-east-as... which led me to conclude that the mortality rate differed.
https://twitter.com/trvrb/status/1257825352660877313
"Both Korber et al and our analysis show no measurable effect on patient outcome. Hence, the hypothesis at this point is entirely in terms of transmissibility rather than severity. 14/16"
The conclusion that mortality is higher comes from the higher death rates in European countries. However, there's a major confounder: when the epidemic exceeds testing capacity, only the most severe cases are tested and counted, and so the denominator in mortality rates (total cases) is inaccurately small. We know this is the case in much of Europe (and NYC): follow-up antibody tests put the number of total infections at ~10x the number of detected cases. That brings the mortality rate back in line with the ~0.5-1% that's been found in populations where everyone was tested.