I 'think' I have 7 somewhere around my sewing room. There is never ever a ripper near at hand when I need it. Which do I prefer? The one that I can find!! Honestly! There are days that finding one is like finding the pot of gold at the end of a rainbow, or hens' teeth in a chicken coop!!
I prefer the larger ergonomic handles, especially the oval ones that might roll in a circular motion but not on to the floor. I have had some success in sharpening the blade by ripping thru a piece of aluminum foil.
If you have access to a Lee Valley outlet or catalogue, they have a phenomenal surgical steel seam ripper. It is amazing!! and you can order replacement blades!! Here is a link:
https://www.leevalley.com/en-ca/shop...eam-ripper-kit