They are similar packages, but both do things differently & have different features, i'm comparing an older version of PPaint with DpaintIV here...
I'm pretty new to it, a big feature that seems missing from my version of PPaint is the ability to lock the background - haven't so far discovered a workaround - Do the newer versions have this?
Being able to adjust an entire indexed palette by HSV in PPaint is a really nice feature that Dpaint lacks, in terms of simple pixelling, they're both pretty much equal, some of PPaint's more advanced image processing features (probably a major selling point/difference to Dpaint) are presumably pretty much redundant though unless you have RTG? - You'd just be better of doing this on a PC(sorry!)
I like both packages, since i'm doing a lot of artwork on the Amiga atm, I may get this.