I bought the Focus Pads just over a year ago. At that time I chose the Focus Pads because they were slightly larger than the Focus A Pads. However I just checked the HiFiMan website to see what the actual size difference is and to my surprise I see that both pads have exactly the same interior dimension. Very odd.
Anyway I seem to have slightly larger than average ears so I chose the (larger??pads) Focus Pads because I don't like tight squishy fitting ear pads. Now that there is no apparent size difference, it would be interesting to hear how these 2 pads differ in sound. In any event I have no complaints with the Focus Pad comfort or sound whatsoever.
I was hoping that @Hansotek could give us a quick comparison and tell us about the differences.