Have used ever technique shown in these pictures.
The most common and what is used by most alteration shops or tailor shops inside of men's stores is the "loop stitch" which is done with a blind stitch machine. Reason to use this; it is the fastest to do and to remove. When you break one stitch you can unravel the entire line of stitching. You can hem a trouser in seconds rather than minutes of time to finish the work. Does not require any special skills to operate a blind stitch machine. You can train a monkey to do this. Don't use this method because we never purchased a blind stitch machine.
Hemming trousers has two issues to address. Restrain the raveling of the cut edge of the cloth and secure the fold up of the hem to the trouser leg. Using the XXX stitch covers the edge to contain the raveling and secures the hem to the trouser leg. Another method shown in these pictures is to fold the cut edge of the hem over to have a finished edge. One benefit of doing this is you can leave more outlet for future needs. Don't like the small amount of bulk it adds that might create a ridge from pressing so I don't do this.
Since the X stitch covers the edge of the hem it secures the hem in a way to keep your toe from snagging the hem and tearing the hem open. This isn't unique to southern Italy, it's done universally, everywhere, anywhere. Exponentially more time consuming than using a blind stitch machine.
A couple of these pictures show the cut edge finished off or lets say overcast with a serging machine to contain the raveling. The Chan hem was then sewn by machine. I do this depending on the client. When the client would be more upset that the hem came open rather than it was sewn by hand or machine. Some clients don't have time or the inclination to deal with maintenance issues with their clothes and this method is full proof for staying secure.
The last picture shows the hem hidden by folding it between the cuff and trouser leg. I learned this method during apprenticeship with tailor from Caraceni/Milano. Raveling is a non issue because the hem is concealed. This method requires more time for basting in the preparation stage and then one straight stitch to finish. I like the clean look. I use this when I want to be an "artiste"!