The Lee Ergo is the hand squeeze ( like the RCBS universal) model.
The Lee Auto Prime is thumb operated.
And new for 2016 is the Auto Bench Prime. Mounts to a bench and operated with a lever by either right or left hand.
So let your aches and pains decide which one to get.
I'm still using the thumb operated old model , and don't have any problems just yet.
For people with achy hands and fingers that bench mounted tool might be just the ticket. Mount it on a board and C-clamp it any where you want inside the house....I've started doing a lot of case prep and even loading inside the heated and cooled house with a Lee Hand press and Auto prime , sitting at this computer desk.
Gary