Concerning Pfizer's vaccine, yes-- many points in its development, and
later revelations about cardiac inflammation, etc-- have come up, with indications that it was swept under the rug, repeatedly. Additionally, many influential people were invested in the Pfizer vaccine, giving it a strong "Too big to fail" mechanical impetus behind it.
Not saying Moderna is free from that, it's not, but Moderna's vaccine technology was .. how to put this.... "overly cautious"... in its development, and went out of its way to ensure very high purity, very high standards for transport and administration, very high quality controls in manufacture, et al-- as it was a groundbreaking testbed for a brand new vaccine type, and thus had to be as free from uncontrolled, and unaccounted for variables as possible, to prove that the technology itself was safe and effective.
Moderna was developing this tech long before covid 19 even thought about being a pandemic-- it has its roots in other conditions and diseases-- and was just rapidly adapted to covid-19, and the pandemic provided the impetus to get the technology into deployment in a short timetable-- The people making it had already been working with mRNA based delivery strategies for quite some time, and knew exactly what they were doing.
Pfizer on the other hand, seems to have been produced with less consideration in mind, with a primary focus on "rapid delivery timetable" and less on "Prove the technology works, is safe, and reliable" like with Moderna's.
J&J's vaccine is based on very old vaccine technologies, namely adenovirus vector based delivery, and is much less selective in what gets put inside the adenovirus, and the adenovirus itself is not terribly selective about where it integrates the payload dna into the host genome. J&J vaccine, and other adenovirus vector vaccines, have been implicated in an increased risk of thrombosis in patients.
There is a reason why I selected, and stuck with, Moderna's vaccination regimen.
It is also VERY important to point out, that despite the above, all of the US vaccines are actually quite effective and safe, in absolute terms. Just, given the choice, I selected the one with the greatest procedural controls, highest quality standards in preparation, and with the least risk of developing complication. (Moderna's mRNA is very specific, and not at all a wide section of viral proteins being produced after inoculation), because I was in a position to do so, and informed about which of the choices best met that safety requirement.