Lets say you have the following snare articulations:
- Edge
- Middle
- Center
- Rim-shot
- Side-stick
Now double the amount of articulations for separate left and right hand samples.
If you do samples with the snares off, you've again doubled the articulations.
The only way you're going to squeeze that into a GM map is to use MIDI controllers to switch articulations.
Depending on the MIDI controller the end user has available, this can be easy or a major pain.
For many users, it's simpler (easier) to have each articulation mapped to a separate MIDI note.
Important to keep in mind... this works with any MIDI controller.

There are no absolutes... it's all a judgement call.