First of all eliminate screw drive openers. They are fine if you have a one piece swing out door found only in warmer climates like California. The chain drive is by far number one in sales and works fine. The belt drive is quieter and almost a must if you have living space above the garage. It would be my first pick. Chamberlain is the worlds largest manufacturer of openers. Last I heard Genie was made by Sanwa Shutter Company. That should tell you something.

why are screwdrives bad? please elaborate

Screwdrive openers are not bad. They have their niche but if you don't have a one piece tilting door you don't live in that niche. Genie knows people are buying their screwdrive openers because they are uninformed and are sure not saying anything.

Of three independent reviews that I've read, the screw drive operation is rated most dependable and quitest. Both Chamberlain and Genie are rated well.

I'm going with Genie because it and Craftsman are all that's available without my driving 80-90 miles.

That rating is wrong. We work on these things all day, belt drives are the quitest and Liftmaster, Craftsman or Chamberlain are the most durable. I would opt for the belt drive.

I just had 2 chamberlain whisper drive openers installed in my garage and I couldn't believe how quiet they are. I got them at Home Depot. They are belt drive and have a battery backup in case of a power outage. I looked at the genie screw drive but decided on the chamberlain because of the battery backup system. The installer(not associated w/HD) told me I made a wise choice. That the belt drive was way quieter than the screw drive.