I don't use Android apps that much, but my experience has been as follows:

• Blackberry seems to check the apk's against their own servers, which should add an extra security
• Android apps work better on Jolla. I haven't come over an Android app that wouldn't work (I'm sure there are some, I just haven't come over them). On the other hand, Android apps on Blackberry break periodically - for example Czech news apps Novinky and iDnes break occasionally (it's a random coincidence to have them both working at the same time), or take minutes to launch.
• Blackberry has a nice option to hide the 'back' button.

This experience is not based on a big sample, but it's what it is. I would say the experience is quite similar in both environment, with Jolla being a bit better (which is quite surprising for me, but it may have something to do with Blackberry not being based on Linux).

EDIT: My experience is based on Z10 and Jolla.