yes, you should always use the influence type of 1 if you are going to scale the objects. When you have the influence set to 2, the mesh gets bad distortion when scaled. This is a bug in maya that has been around as far as I know since version 3.
The difference between influences 1 and 2 is that 1 is for vertices, and 2 is for faces. with 2 you can have a smaller max distance, with better performance, but you can't scale. Again the bug in maya.
A problem I'm dealing with today is having a referenced character with wrap deformers, that ARE scaled to fit scenes. I'm finding that with a influence 1 setting, the mesh is getting rippling effects. Both meshes are polys BTW. When I change the influence type to 2, the rippling goes away. But I need to scale my characters in other scenes! Terrible problem, as characters aren't finished with materials and blendshapes and all that. I may have to just resort to importing to those scenes when all materials and blendshapes are done.
Hopes this helps ya.