From the J&J trial results [1]:

Vaccine efficacy (VE) against central laboratory-confirmed moderate to severe/critical COVID19 across all geographic areas in which the trial was conducted was 66.9% (95% CI 59.0, 73.4) when considering cases occurring at least 14 days after the single-dose vaccination and 66.1% (55.0, 74.8) when considering cases occurring at least 28 days after vaccination.

I have seen estimates as low as 40-something % for single doses of the mRNA vaccines, but this may have been an underestimate caused by only considering the first two weeks after inoculation. Given enough time for immunity to fully set in, the real number may be over 90% [2].

HOWEVER, those numbers all refer to symptomatic disease. Prevention of hospitalization and death was 100% in the J&J trial.

[1] https://www.fda.gov/media/146217/download

[2] https://www.nejm.org/doi/full/10.1056/NEJMc2036242

There’s a big difference between 2 weeks and 1 month, we know that now. Also the main concerns of the article are long term protection and protection against new variants. Both of these issues can wait until more people are vaccinated, and again we don’t have long term data on J&J vaccine, and I don’t see why it would be better than the mRNA vaccines.

I wonder this too, the non-mRNA vaccines are inferior technology

I'll take inferior and well tested over superior and untested any time.

which has nothing to do with determining efficacy of a single shot mRNA vaccine and a single shot non-mRNA vaccine

Inferior in the same way your chrome sandbox is inferior to node because it can’t access system files.