The phrase "main difference" refers to the biggest or most significant distinction between two or more things. It indicates the most notable contrast or variation that sets them apart from each other. Full definition
The other main difference between cats and dogs is that heartworm can be treated in dogs, but it can not be treated in cats. (vippetcare.com)
The only main difference in a regular and email based cover letter is that the former tends to be a bit longer as compared to the later. (coverlettersandresume.com)
The other main difference with industry is the emphasis on the two - way selling process. (sciencemag.org)