In my humble opinion both flowering and purple leaf plum are outstanding bow woods.
Strong in compression and tension, easily moved with heat, durable, beautiful, easy to work, easy to harvest and suitable for many designs (from 48" bendy handle statics to 68 deep bellied long bows and everything in between).
For ease of building, flexibility in design options, forgiving characteristics, and down right "bowy-ness" (an important characteristic that I totally made up), I honestly can't think of a wood (including my limited experience with Osage and Yew) that I would rather build a bow out of.
8 times out of 10, for me, its Plum.
Gabe