I started with rabbet planes about 10 years ago when I was trimming the tumblehome on my original Nymph. They allow you to plane installed strips right up next to the forms.
My first was the Lie Nielsen rabbet block plane. It is a really nice tool, but I found I was using my fingers as a fence to help hold it at the right spacing depending on the strip thickness.
While teaching up at WoodenBoat School, I found their secret stash of tools that had been provided to the magazine for review. Included were a variety of rabbet planes including shoulder planes and most intriguing was a Veritas, side rabbet with blades on both sides and an adjustable fence. I quickly picked up one of these.
A few years later I was looking through some used tools and found the Stanley #79 side rabbet. They usually come with a fence, but I had to make one for mine.
Playing with these were what inspired the Robots-Bevel.
I use whatever is closest at hand each different version having slight advantages in different situations.