[wareotie]

With C-b you have less movement, C-a moves your hand in a weird form which creates pain in the hand. Apart from that, I use only my left hand to press C-b.

C-a is the default one in Screen but as far as I remember C-b is the default one in Tmux since the beginning of the project.

C-x is a bad idea too, because is another shortcut in bash (C-x + e bring up the $EDITOR). I think C-b is a good choice.

The only thing I change in tmux is the pane and windows number (I prefer to start in 1 instead of 0 because I can type with less movement).