I don't think the change of buffer has that much of an effect, as long as the pH is maintained and it is not toxic for Agrobacterium. For infiltration of Arabidopsis flower buds we use 0.5X MS: http://link.springer.com/article/10.1007%2FBF02773350
For infiltration of tobacco leaves also MES buffer is used: http://naldc.nal.usda.gov/download/29286/PDF