I think I'm a little late for this topic : but I think it maybe just people's preference in what you use. My wife prefers chopped, where as I prefer plums 
 Chopped I find are a little sharper in taste I think. Another difference I have noticed is that in chopped tins, you can often find skin, where in plum, you don't.
 For me, no skin is better for a good smooth base.