Start with the drive, because it decides most of what you will hear about the opener later. Garage door openers use a chain, a belt, a screw, or a direct drive, and each one moves the door in its own way. The drive sets how loud the unit runs, how it wears, how often it asks for attention, and how it sits in the space above the door.
A chain drive is the traditional form. It is usually the most audible option, which matters if the garage shares a wall with a bedroom or a home office. A belt drive runs quieter and is often described as smoother in the room below. A screw drive has a threaded rod that the carriage rides along, which tends to need periodic lubrication. A direct drive puts the motor on the rail itself, so there is less belt or chain to tension, but the unit sits differently on the ceiling.
When you compare two openers, sort them by drive type first and then by the details inside each type. Ask for the sound level stated for the room where you will actually hear it, not only as a general figure. Ask what the manual says about lubrication and tension, and who in your area can do that work. Ask how the safety reverse is tested and what the wall control needs. Ask the seller to put every claim in writing, including the warranty period and how a claim is made. Do not accept a claim that is only spoken.
Keep the comparison on a sheet you can see. Write down the drive, the sound level for your room, the maintenance the manual calls for, and the questions the seller could not answer. The column with the most blank lines is usually the one to ask more about before you decide. For the typical service life of this system and when to start planning, see the garage door opener page on this site.