Left-hand mouse all the way.
I am a totally right-handed person, and used a right-hand mouse exclusively (since the 1980s) until a couple of years ago.
At some point, I read a recommendation for left-hand mousing and it just "clicked" so I tried it. No regrets.
I am an old man, so it was painful for a week and awkward for a month, but after that, smooth sailing.
Enter the Wow Joy Pen mouse about a year ago. For whatever reasons, I tried it and found the most beautiful mouse of all time. Other vertical mice, like the horrible Evoluent, are just plain wrong (I have not yet given the Anker a spin). So why is there only right hand Joy?
Today, I employ an ambidextrous mouse (Microsoft Optical 1) on the left and the Wow Joy Pen on the right. If you have the desk space, dual mousing is very handy and convenient. That is the way to go.
So let's just wait until Joy makes the left-hand version.