What is subpicture and should I include it when I copy a movie?
Knowing what it is will generally answer the question as to whether you want to include it or not as part of the rip.
In most cases, the subpicture(s) are the subtitles in various languages (if you don’t speak English and the sountrack is in English).
In some select cases, where various camera angles are offered as part of the DVD package, the subpictures can also be those extra camera angles.
As to whether you want to keep them or not, the choice is yours.