There’s a difference in fit although they are similar. Dainese tends to come up small and the legs are long. Alpinestars for some reason end up being baggy round the backside on most people.
Just depends on your body shape really, try them on and see what you think.
I wanted a second set of leathers so bought Dianese in the same size as my AS but was a little too tight to be comfortable all day. Were a used pair so just re-sold.