Blennies are pretty good except for with other blennies and firefish. But I’d go with the gramma as they stand up for themselves without being as aggressive themselves.
I went with the royal gramma! Everyone's been very well behaved so far; hopefully that continues as they settle in.
My LFS had both the royal gramma and an orchid dottyback, but their dottyback was housed in a tank with a springer's damsel that was about the size of mine, and that dottyback was a total jerk to the poor damsel. It helped my decision along, I think. Thanks for the suggestion!