I am happy about bundle package, but I am lesser happy about Canonical/Ubuntu stuff, anyway flatpack is older and more reliable than snap, is a community project and not a secret project by a crew of fanboys, most important is not hosted in a proprietary server and you don't need to subscribe any CLA. If I have to choice which bundle of course flatpak is my choice.
However when snap is under a huge marketing campaign for not what reason, I feel these bundle software are a good opportunity for me to try some software which is really impossible to compile, I think is more reliable using a bundle instead to do: make, make install, make uninstall. Now I could try easily Gimp, Krita or Scribus development branch without going crazy because I am not able to compile them.
I already post this article in an other post but is good to read here as well: http://www.infoworld.com/article/308626 ... ource.html
EDIT
I would add this, only the older distros as problem with different version of packages and libraries guixSD allows different version of packages and libraries stored in the home folder.