The Postal Service has been changing its cancellation marks. As you might expect, I'm a fan of the old way. This cancellation is much like letterpress printing. The printed image is raised and it actually touches the surface it prints on. The cancellation looks good, and the date and city information is easy to read.
The new inkjet cancellation keeps the wavy line of the original, but doesn't retain the circle with the date/city info. The dot pattern isn't tight enough to make small, readable lettering. So the letters are quite large. I'm guessing it's faster to run mail through the inkjet cancel machine because the printer doesn't actually have to touch the piece of mail -- it just sprays the surface as it goes by.
Probably the major advantage of the inkjet cancellation is it that it's programmable. Someone decides to promote Arbor Day or something? It's just an easy computer change. Still looks bad with the sloppy dot pattern, but it's quicker and easier than making a new, physical, cancel marker.
The biggest disadvantage of the inkjet cancellation is keeping the thing in focus. Yikes!