Similarities are greater than differences, this being the one major difference:
Storage requirements
Both of these vaccines require an elaborate cold chain, the term used to describe the conditions under which vaccines must be stored during distribution and when they are in the doctors’ offices, pharmacies, or public health clinics where they’ll be administered.
But the Moderna vaccine will be far easier to use than Pfizer’s. For starters, Moderna’s must be shipped at -4 Fahrenheit; Pfizer’s must be shipped and stored at -94 Fahrenheit. The former is the temperature of a regular refrigerator freezer; the latter requires special ultra-cold freezers that need to be topped up with dry ice every five days. Doctors’ offices do not have ultracold freezers; neighborhood pharmacies don’t either.
After thawing, a vial of the Pfizer vaccine must be used within five days; Moderna’s is stable at fridge temperature for 30 days and at room temperature for 12 hours.
Contradicting Melinda Gates' ignorant whine (about rich nations hogging the vaccines), neither vaccine is suitable for third-world usage -parts of the world where electric power is intermittent and proper cold transport and storage is not widely or reliably available.