As far as I can tell the difference between the pfizer and moderna vaccines are negligible. The results of differences in their testing procedure and conditions - the stuff you’re getting is basically the same. So, unless you’re (in my opinion) wrongly calculating the risk from a vaccine as larger than the risk from the disease, the best shot is the one you can get soonest.
Given a choice, I would choose Pzifer over Moderna, since it has fewer side effects [1], but otherwise they're both good and protect approximately equally against known variants. I wouldn't choose J&J or AZ if my age is below 60yo because of a very low risk of deadly side effects (clots).
Edit: unless my BMI > 30, in which case any vaccine is better than no vaccine, because of the increased risks of covid-19 on high BMI.
