The larger one has slots 2.5" apart. Great for cutting your own jelly roll strips, charms and layer cakes. Also, this one will span the entire piece of fabric as it comes from the bolt, which is convenient, but you do need to have a large cutting mat and a place to use it.
The Plus has slits every half inch, so that's good for sub cutting smaller pieces. If you can double fold fabric from the blot you can cut yardage, but I am not very sucessful.
If you work mainly with full yardage, I would go with the Pro, if you use mostly FQ's then the Plus is a good choice.