PC vs Mac Acrobat DC to reduce/compress files

Hey there,

I use a Mac and my colleague has a PC. I used the Reduce File Size and got a file down to 4.6 MB. It wasn't sufficient enough of a file reduction for an application we use to accept the file. My colleague on the PC used Compress PDF and got it down to 4 MB.

If the function is the same on both machines, why the difference in the performance? What is the best method to reduce a PDF file size as much as possible on a Mac?